Package io.debezium.text

Class TokenStream

java.lang.Object
io.debezium.text.TokenStream
@NotThreadSafe public class TokenStream extends Object
A foundation for basic parsers that tokenize input content and allows parsers to easily access and use those tokens. A TokenStream object literally represents the stream of TokenStream.Token objects that each represent a word, symbol, comment or other lexically-relevant piece of information. This simple framework makes it very easy to create a parser that walks through (or "consumes") the tokens in the order they appear and do something useful with that content (usually creating another representation of the content, such as some domain-specific Abstract Syntax Tree or object model).

The parts

This simple framework consists of a couple of pieces that fit together to do the whole job of parsing input content.

The TokenStream.Tokenizer is responsible for consuming the character-level input content and constructing TokenStream.Token objects for the different words, symbols, or other meaningful elements contained in the content. Each Token object is a simple object that records the character(s) that make up the token's value, but it does this in a very lightweight and efficient way by pointing to the original character stream. Each token can be assigned a parser-specific integral token type that may make it easier to do quickly figure out later in the process what kind of information each token represents. The general idea is to keep the Tokenizer logic very simple, and very often TokenStream.Tokenizers will merely look for the different kinds of characters (e.g., symbols, letters, digits, etc.) as well as things like quoted strings and comments. However, TokenStream.Tokenizers are never called by the parser, but instead are always given to the TokenStream that then calls the Tokenizer at the appropriate time.

The TokenStream is supplied the input content, a Tokenizer implementation, and a few options. Its job is to prepare the content for processing, call the Tokenizer implementation to create the series of Token objects, and then provide an interface for walking through and consuming the tokens. This interface makes it possible to discover the value and type of the current token, and consume the current token and move to the next token. Plus, the interface has been designed to make the code that works with the tokens to be as readable as possible.

The final component in this framework is the Parser. The parser is really any class that takes as input the content to be parsed and that outputs some meaningful information. The parser will do this by defining the Tokenizer, constructing a TokenStream object, and then using the TokenStream to walk through the sequence of Tokens and produce some meaningful representation of the content. Parsers can create instances of some object model, or they can create a domain-specific Abstract Syntax Tree representation.

The benefit of breaking the responsibility along these lines is that the TokenStream implementation is able to encapsulate quite a bit of very tedious and very useful functionality, while still allowing a lot of flexibility as to what makes up the different tokens. It also makes the parser very easy to write and read (and thus maintain), without placing very many restrictions on how that logic is to be defined. Plus, because the TokenStream takes responsibility for tracking the positions of every token (including line and column numbers), it can automatically produce meaningful errors.

Consuming tokens

A parser works with the tokens on the TokenStream using a variety of methods:

  • The start() method must be called before any of the other methods. It performs initialization and tokenization, and prepares the internal state by finding the first token and setting an internal current token reference.
  • The hasNext() method can be called repeatedly to determine if there is another token after the current token. This is often useful when an unknown number of tokens is to be processed, and behaves very similarly to the Iterator.hasNext() method.
  • The consume() method returns the value of the current token and moves the current token pointer to the next available token.
  • The consume(String) and consume(char) methods look at the current token and ensure the token's value matches the value supplied as a method parameter, or they throw a ParsingException if the values don't match. The consume(int) method works similarly, except that it attempts to match the token's type. And, the consume(String, String...) is a convenience method that is equivalent to calling consume(String) for each of the arguments.
  • The canConsume(String) and canConsume(char) methods look at the current token and check whether the token's value matches the value supplied as a method parameter. If there is a match, the method advances the current token reference and returns true. Otherwise, the current token does not match and the method returns false without advancing the current token reference or throwing a ParsingException. Similarly, the canConsume(int) method checks the token's type rather than the value, consuming the token and returning true if there is a match, or just returning false if there is no match. The canConsume(String, String...) method determines whether all of the supplied values can be consumed in the given order.
  • The matches(String) and matches(char) methods look at the current token and check whether the token's value matches the value supplied as a method parameter. The method then returns whether there was a match, but does not advance the current token pointer. Similarly, the matches(int) method checks the token's type rather than the value. The matches(String, String...) method is a convenience method that is equivalent to calling matches(String) for each of the arguments, and the matches(int, int...) method is a convenience method that is equivalent to calling matches(int) for each of the arguments.
  • The matchesAnyOf(String, String...) methods look at the current token and check whether the token's value matches at least one of the values supplied as method parameters. The method then returns whether there was a match, but does not advance the current token pointer. Similarly, the matchesAnyOf(int, int...) method checks the token's type rather than the value.

    • With these methods, it's very easy to create a parser that looks at the current token to decide what to do, and then consume that token, and repeat this process.

    Example parser

    Here is an example of a very simple parser that parses very simple and limited SQL SELECT and DELETE statements, such as SELECT * FROM Customers or SELECT Name, StreetAddress AS Address, City, Zip FROM Customers or DELETE FROM Customers WHERE Zip=12345: 

     public class SampleSqlSelectParser {
     public List<Statement> parse( String ddl ) {
         TokenStream tokens = new TokenStream(ddl, new SqlTokenizer(), false);
         List<Statement> statements = new LinkedList<Statement>();
         token.start();
         while (tokens.hasNext()) {
             if (tokens.matches("SELECT")) {
                 statements.add(parseSelect(tokens));
             } else {
                 statements.add(parseDelete(tokens));
             }
         }
         return statements;
     }

     protected Select parseSelect( TokenStream tokens ) throws ParsingException {
         tokens.consume("SELECT");
         List<Column> columns = parseColumns(tokens);
         tokens.consume("FROM");
         String tableName = tokens.consume();
         return new Select(tableName, columns);
     }

     protected List<Column> parseColumns( TokenStream tokens ) throws ParsingException {
         List<Column> columns = new LinkedList<Column>();
         if (tokens.matches('*')) {
             tokens.consume(); // leave the columns empty to signal wildcard
         } else {
             // Read names until we see a ','
             do {
                 String columnName = tokens.consume();
                 if (tokens.canConsume("AS")) {
                     String columnAlias = tokens.consume();
                     columns.add(new Column(columnName, columnAlias));
                 } else {
                     columns.add(new Column(columnName, null));
                 }
             } while (tokens.canConsume(','));
         }
         return columns;
     }

     protected Delete parseDelete( TokenStream tokens ) throws ParsingException {
         tokens.consume("DELETE", "FROM");
         String tableName = tokens.consume();
         tokens.consume("WHERE");
         String lhs = tokens.consume();
         tokens.consume('=');
         String rhs = tokens.consume();
         return new Delete(tableName, new Criteria(lhs, rhs));
     }
  }
  public abstract class Statement { ... }
  public class Query extends Statement { ... }
  public class Delete extends Statement { ... }
  public class Column { ... }
    This example shows an idiomatic way of writing a parser that is stateless and thread-safe. The parse(...) method takes the input as a parameter, and returns the domain-specific representation that resulted from the parsing. All other methods are utility methods that simply encapsulate common logic or make the code more readable.

    In the example, the parse(...) first creates a TokenStream object (using a Tokenizer implementation that is not shown), and then loops as long as there are more tokens to read. As it loops, if the next token is "SELECT", the parser calls the parseSelect(...) method which immediately consumes a "SELECT" token, the names of the columns separated by commas (or a '*' if there all columns are to be selected), a "FROM" token, and the name of the table being queried. The parseSelect(...) method returns a Select object, which then added to the list of statements in the parse(...) method. The parser handles the "DELETE" statements in a similar manner.

    Case sensitivity

    Very often grammars to not require the case of keywords to match. This can make parsing a challenge, because all combinations of case need to be used. The TokenStream framework provides a very simple solution that requires no more effort than providing a boolean parameter to the constructor.

    When a false value is provided for the the caseSensitive parameter, the TokenStream performs all matching operations as if each token's value were in uppercase only. This means that the arguments supplied to the match(...), canConsume(...), and consume(...) methods should be upper-cased. Note that the actual value of each token remains the actual case as it appears in the input.

    Of course, when the TokenStream is created with a true value for the caseSensitive parameter, the matching is performed using the actual value as it appears in the input content

    Whitespace

    Many grammars are independent of lines breaks or whitespace, allowing a lot of flexibility when writing the content. The TokenStream framework makes it very easy to ignore line breaks and whitespace. To do so, the Tokenizer implementation must simply not include the line break character sequences and whitespace in the token ranges. Since none of the tokens contain whitespace, the parser never has to deal with them.

    Of course, many parsers will require that some whitespace be included. For example, whitespace within a quoted string may be needed by the parser. In this case, the Tokenizer should simply include the whitespace characters in the tokens.

    Writing a Tokenizer

    Each parser will likely have its own TokenStream.Tokenizer implementation that contains the parser-specific logic about how to break the content into token objects. Generally, the easiest way to do this is to simply iterate through the character sequence passed into the tokenize(...) method, and use a switch statement to decide what to do.

    Here is the code for a very basic Tokenizer implementation that ignores whitespace, line breaks and Java-style (multi-line and end-of-line) comments, while constructing single tokens for each quoted string. 

     public class BasicTokenizer implements Tokenizer {
     public void tokenize(CharacterStream input,
                          Tokens tokens)
             throws ParsingException {
         while (input.hasNext()) {
             char c = input.next();
             switch (c) {
                 case ' ':
                 case '\t':
                 case '\n':
                 case '\r':
                     // Just skip these whitespace characters ...
                     break;
                 case '-':
                 case '(':
                 case ')':
                 case '{':
                 case '}':
                 case '*':
                 case ',':
                 case ';':
                 case '+':
                 case '%':
                 case '?':
                 case '$':
                 case '[':
                 case ']':
                 case '!':
                 case '<':
                 case '>':
                 case '|':
                 case '=':
                 case ':':
                     tokens.addToken(input.index(), input.index() + 1, SYMBOL);
                     break;
                 case '.':
                     tokens.addToken(input.index(), input.index() + 1, DECIMAL);
                     break;
                 case '\"':
                     int startIndex = input.index();
                     Position startingPosition = input.position();
                     boolean foundClosingQuote = false;
                     while (input.hasNext()) {
                         c = input.next();
                         if (c == '\\' && input.isNext('"')) {
                             c = input.next(); // consume the ' character since it is escaped
                         } else if (c == '"') {
                             foundClosingQuote = true;
                             break;
                         }
                     }
                     if (!foundClosingQuote) {
                         throw new ParsingException(startingPosition, "No matching closing double quote found");
                     }
                     int endIndex = input.index() + 1; // beyond last character read
                     tokens.addToken(startIndex, endIndex, DOUBLE_QUOTED_STRING);
                     break;
                 case '\'':
                     startIndex = input.index();
                     startingPosition = input.position();
                     foundClosingQuote = false;
                     while (input.hasNext()) {
                         c = input.next();
                         if (c == '\\' && input.isNext('\'')) {
                             c = input.next(); // consume the ' character since it is escaped
                         } else if (c == '\'') {
                             foundClosingQuote = true;
                             break;
                         }
                     }
                     if (!foundClosingQuote) {
                         throw new ParsingException(startingPosition, "No matching closing single quote found");
                     }
                     endIndex = input.index() + 1; // beyond last character read
                     tokens.addToken(startIndex, endIndex, SINGLE_QUOTED_STRING);
                     break;
                 case '/':
                     startIndex = input.index();
                     if (input.isNext('/')) {
                         // End-of-line comment ...
                         boolean foundLineTerminator = false;
                         while (input.hasNext()) {
                             c = input.next();
                             if (c == '\n' || c == '\r') {
                                 foundLineTerminator = true;
                                 break;
                             }
                         }
                         endIndex = input.index(); // the token won't include the '\n' or '\r' character(s)
                         if (!foundLineTerminator) ++endIndex; // must point beyond last char
                         if (c == '\r' && input.isNext('\n')) input.next();
                         if (useComments) {
                             tokens.addToken(startIndex, endIndex, COMMENT);
                         }
                     } else if (input.isNext('*')) {
                         // Multi-line comment ...
                         while (input.hasNext() && !input.isNext('*', '/')) {
                             c = input.next();
                         }
                         if (input.hasNext()) input.next(); // consume the '*'
                         if (input.hasNext()) input.next(); // consume the '/'
                         if (useComments) {
                             endIndex = input.index() + 1; // the token will include the '/' and '*' characters
                             tokens.addToken(startIndex, endIndex, COMMENT);
                         }
                     } else {
                         // just a regular slash ...
                         tokens.addToken(startIndex, startIndex + 1, SYMBOL);
                     }
                     break;
                 default:
                     startIndex = input.index();
                     // Read until another whitespace/symbol/decimal/slash is found
                     while (input.hasNext() && !(input.isNextWhitespace() || input.isNextAnyOf("/.-(){}*,;+%?$[]!<>|=:"))) {
                         c = input.next();
                     }
                     endIndex = input.index() + 1; // beyond last character that was included
                     tokens.addToken(startIndex, endIndex, WORD);
             }
         }
     }
 }
    TokenStream.Tokenizers with exactly this behavior can actually be created using the basicTokenizer(boolean) method. So while this very basic implementation is not meant to be used in all situations, it may be useful in some situations.

    Author:
    Randall Hauch, Horia Chiorean, Daniel Kelleher

    • Field Details

    • Constructor Details

    • Method Details

      • start

        public TokenStream start() throws ParsingException
        Begin the token stream, including (if required) the tokenization of the input content.
        Returns:
        this object for easy method chaining; never null
        Throws:
        ParsingException - if an error occurs during tokenization of the content

      • initializeTokens

        protected List<TokenStream.Token> initializeTokens(List<TokenStream.Token> tokens)
        Method to allow subclasses to pre-process the set of tokens and return the correct tokens to use. The default behavior is to simply return the supplied tokens.
        Parameters:
        tokens - the tokens
        Returns:
        list of tokens.

      • rewind

        public void rewind()
        Method to allow tokens to be re-used from the start without re-tokenizing content.

      • mark

        public TokenStream.Marker mark()
        Obtain a marker that records the current position so that the stream can be rewind(Marker) back to the mark even after having been advanced beyond the mark.
        Returns:
        the marker; never null
        Throws:
        IllegalStateException - if this method was called before the stream was started
        NoSuchElementException - if there are no more tokens

      • rewind

        public boolean rewind(TokenStream.Marker marker)
        Reset the stream back to the position described by the supplied marker. This method does nothing if the mark is invalid. For example, it is not possible to advance the token stream beyond the current position.
        Parameters:
        marker - the marker
        Returns:
        true if the token stream was reset, or false if the marker was invalid
        See Also:

      • advance

        public boolean advance(TokenStream.Marker marker)
        Advance the stream back to the position described by the supplied marker. This method does nothing if the mark is invalid. For example, it is not possible to rewind the token stream beyond the current position.
        Parameters:
        marker - the marker
        Returns:
        true if the token stream was advanced, or false if the marker was invalid
        See Also:

      • previousPosition

        public Position previousPosition()
        Get the position of the previous token.
        Returns:
        the previous token's position; never null
        Throws:
        IllegalStateException - if this method was called before the stream was started
        NoSuchElementException - if there is no previous token

      • previousPosition

        public Position previousPosition(int count)
        Get the position of a token earlier in the stream from the current position.
        Parameters:
        count - the number of tokens before the current position (e.g., 1 for the previous position)
        Returns:
        the previous token's position; never null
        Throws:
        IllegalStateException - if this method was called before the stream was started
        NoSuchElementException - if there is no previous token

      • nextPosition

        public Position nextPosition()
        Get the position of the next (or current) token.
        Returns:
        the current token's position; never null
        Throws:
        IllegalStateException - if this method was called before the stream was started
        NoSuchElementException - if there is no previous token

      • consume

        public String consume() throws ParsingException, IllegalStateException
        Return the value of this token and move to the next token.
        Returns:
        the value of the current token
        Throws:
        ParsingException - if there is no such token to consume
        IllegalStateException - if this method was called before the stream was started

      • throwNoMoreContent

        protected void throwNoMoreContent() throws ParsingException
        Throws:
        ParsingException

      • peek

        public String peek() throws IllegalStateException
        Throws:
        IllegalStateException

      • consume

        public TokenStream consume(String expected) throws ParsingException, IllegalStateException
        Attempt to consume this current token as long as it matches the expected value, or throw an exception if the token does not match.

        The ANY_VALUE constant can be used in the expected values as a wildcard.

        Parameters:
        expected - the expected value of the current token
        Returns:
        this token stream instance so callers can chain together methods; never null
        Throws:
        ParsingException - if the current token doesn't match the supplied value
        IllegalStateException - if this method was called before the stream was started

      • consume

        public TokenStream consume(char expected) throws ParsingException, IllegalStateException
        Attempt to consume this current token as long as it matches the expected character, or throw an exception if the token does not match.
        Parameters:
        expected - the expected character of the current token
        Returns:
        this token stream instance so callers can chain together methods; never null
        Throws:
        ParsingException - if the current token doesn't match the supplied value
        IllegalStateException - if this method was called before the stream was started

      • consume

        public TokenStream consume(int expectedType) throws ParsingException, IllegalStateException
        Attempt to consume this current token as long as it matches the expected character, or throw an exception if the token does not match.

        The ANY_TYPE constant can be used in the expected values as a wildcard.

        Parameters:
        expectedType - the expected token type of the current token
        Returns:
        this token stream instance so callers can chain together methods; never null
        Throws:
        ParsingException - if the current token doesn't match the supplied value
        IllegalStateException - if this method was called before the stream was started

      • consume

        public TokenStream consume(String expected, String... expectedForNextTokens) throws ParsingException, IllegalStateException
        Attempt to consume this current token as the next tokens as long as they match the expected values, or throw an exception if the token does not match.

        The ANY_VALUE constant can be used in the expected values as a wildcard.

        Parameters:
        expected - the expected value of the current token
        expectedForNextTokens - the expected values of the following tokens
        Returns:
        this token stream instance so callers can chain together methods; never null
        Throws:
        ParsingException - if the current token doesn't match the supplied value
        IllegalStateException - if this method was called before the stream was started

      • consume

        public TokenStream consume(String[] nextTokens) throws ParsingException, IllegalStateException
        Attempt to consume this current token as the next tokens as long as they match the expected values, or throw an exception if the token does not match.

        The ANY_VALUE constant can be used in the expected values as a wildcard.

        Parameters:
        nextTokens - the expected values for the next tokens
        Returns:
        this token stream instance so callers can chain together methods; never null
        Throws:
        ParsingException - if the current token doesn't match the supplied value
        IllegalStateException - if this method was called before the stream was started

      • consume

        public TokenStream consume(Iterable<String> nextTokens) throws ParsingException, IllegalStateException
        Attempt to consume this current token as the next tokens as long as they match the expected values, or throw an exception if the token does not match.

        The ANY_VALUE constant can be used in the expected values as a wildcard.

        Parameters:
        nextTokens - the expected values for the next tokens
        Returns:
        this token stream instance so callers can chain together methods; never null
        Throws:
        ParsingException - if the current token doesn't match the supplied value
        IllegalStateException - if this method was called before the stream was started

      • consumeAnyOf

        public String consumeAnyOf(int... typeOptions) throws IllegalStateException
        Consume and return the next token that must match one of the supplied values.
        Parameters:
        typeOptions - the options for the type of the current token
        Returns:
        the token that was consumed and that matches one of the supplied options
        Throws:
        ParsingException - if the current token doesn't match the supplied value
        IllegalStateException - if this method was called before the stream was started

      • consumeAnyOf

        public String consumeAnyOf(String... options) throws IllegalStateException
        Consume and return the next token that must match one of the supplied values.
        Parameters:
        options - the additional options for the value of the current token
        Returns:
        the token that was consumed and that matches one of the supplied options
        Throws:
        ParsingException - if the current token doesn't match the supplied value
        IllegalStateException - if this method was called before the stream was started

      • consumeThrough

        public TokenStream consumeThrough(char expected) throws ParsingException, IllegalStateException
        Attempt to consume all tokens until the specified token is consumed, and then stop. If it is not found, then the token stream is left untouched and a ParsingException is thrown.

        The ANY_VALUE constant can be used in the expected values as a wildcard.

        Parameters:
        expected - the token that is to be found
        Returns:
        this token stream instance so callers can chain together methods; never null
        Throws:
        ParsingException - if the specified token cannot be found
        IllegalStateException - if this method was called before the stream was started

      • consumeThrough

        public TokenStream consumeThrough(char expected, char skipMatchingTokens) throws ParsingException, IllegalStateException
        Attempt to consume all tokens until the specified token is consumed, and then stop. If it is not found, then the token stream is left untouched and a ParsingException is thrown.

        The ANY_VALUE constant can be used in the expected values as a wildcard.

        Parameters:
        expected - the token that is to be found
        skipMatchingTokens - the token that, if found, should result in skipping expected once for each occurrence of skipMatchingTokens; may be null
        Returns:
        this token stream instance so callers can chain together methods; never null
        Throws:
        ParsingException - if the specified token cannot be found
        IllegalStateException - if this method was called before the stream was started

      • consumeThrough

        public TokenStream consumeThrough(String expected) throws ParsingException, IllegalStateException
        Attempt to consume all tokens until the specified token is consumed, and then stop. If it is not found, then the token stream is left untouched and a ParsingException is thrown.

        The ANY_VALUE constant can be used in the expected values as a wildcard.

        Parameters:
        expected - the token that is to be found
        Returns:
        this token stream instance so callers can chain together methods; never null
        Throws:
        ParsingException - if the specified token cannot be found
        IllegalStateException - if this method was called before the stream was started

      • consumeThrough

        public TokenStream consumeThrough(String expected, String skipMatchingTokens) throws ParsingException, IllegalStateException
        Attempt to consume all tokens until the specified token is consumed, and then stop. If it is not found, then the token stream is left untouched and a ParsingException is thrown.

        The ANY_VALUE constant can be used in the expected values as a wildcard.

        Parameters:
        expected - the token that is to be found
        skipMatchingTokens - the token that, if found, should result in skipping expected once for each occurrence of skipMatchingTokens; may be null
        Returns:
        this token stream instance so callers can chain together methods; never null
        Throws:
        ParsingException - if the specified token cannot be found
        IllegalStateException - if this method was called before the stream was started

      • consumeUntil

        public TokenStream consumeUntil(char expected) throws ParsingException, IllegalStateException
        Attempt to consume all tokens until the specified token is found, and then stop before consuming that token. If it is not found, then the token stream is left untouched and a ParsingException is thrown.

        The ANY_VALUE constant can be used in the expected values as a wildcard.

        Parameters:
        expected - the token that is to be found
        Returns:
        this token stream instance so callers can chain together methods; never null
        Throws:
        ParsingException - if the specified token cannot be found
        IllegalStateException - if this method was called before the stream was started

      • consumeUntil

        public TokenStream consumeUntil(char expected, char skipMatchingTokens) throws ParsingException, IllegalStateException
        Attempt to consume all tokens until the specified token is found, and then stop before consuming that token. If it is not found, then the token stream is left untouched and a ParsingException is thrown.

        The ANY_VALUE constant can be used in the expected values as a wildcard.

        Parameters:
        expected - the token that is to be found
        skipMatchingTokens - the token that, if found, should result in skipping expected once for each occurrence of skipMatchingTokens
        Returns:
        this token stream instance so callers can chain together methods; never null
        Throws:
        ParsingException - if the specified token cannot be found
        IllegalStateException - if this method was called before the stream was started

      • consumeUntil

        public TokenStream consumeUntil(String expected) throws ParsingException, IllegalStateException
        Attempt to consume all tokens until the specified token is found, and then stop before consuming that token. If it is not found, then the token stream is left untouched and a ParsingException is thrown.

        The ANY_VALUE constant can be used in the expected values as a wildcard.

        Parameters:
        expected - the token that is to be found
        Returns:
        this token stream instance so callers can chain together methods; never null
        Throws:
        ParsingException - if the specified token cannot be found
        IllegalStateException - if this method was called before the stream was started

      • consumeUntil

        public TokenStream consumeUntil(String expected, String... skipMatchingTokens) throws ParsingException, IllegalStateException
        Attempt to consume all tokens until the specified token is found, and then stop before consuming that token. If it is not found, then the token stream is left untouched and a ParsingException is thrown.

        The ANY_VALUE constant can be used in the expected values as a wildcard.

        Parameters:
        expected - the token that is to be found
        skipMatchingTokens - the token that, if found, should result in skipping expected once for each occurrence of skipMatchingTokens; may be null
        Returns:
        this token stream instance so callers can chain together methods; never null
        Throws:
        ParsingException - if the specified token cannot be found
        IllegalStateException - if this method was called before the stream was started

      • consumeUntilEndOrOneOf

        public TokenStream consumeUntilEndOrOneOf(String... stopTokens) throws ParsingException, IllegalStateException
        Consume the token stream until one of the stop tokens or the end of the stream is found.
        Parameters:
        stopTokens - the stop tokens; may not be null
        Returns:
        this token stream instance so callers can chain together methods; never null
        Throws:
        ParsingException - if none of the specified tokens can be found
        IllegalStateException - if this method was called before the stream was started

      • canConsumeInteger

        public boolean canConsumeInteger(IntConsumer consumer) throws IllegalStateException
        Attempt to consume this current token if it can be parsed as an integer, and return whether this method was indeed able to consume the token.
        Parameters:
        consumer - the function that should be called with the integer value if the current token token could be parsed
        Returns:
        true if the current token did match and was consumed, or false if the current token did not match and therefore was not consumed
        Throws:
        IllegalStateException - if this method was called before the stream was started

      • canConsumeBoolean

        public boolean canConsumeBoolean(BooleanConsumer consumer) throws IllegalStateException
        Attempt to consume this current token if it can be parsed as a boolean, and return whether this method was indeed able to consume the token.
        Parameters:
        consumer - the function that should be called with the boolean value if the current token token could be parsed
        Returns:
        true if the current token did match and was consumed, or false if the current token did not match and therefore was not consumed
        Throws:
        IllegalStateException - if this method was called before the stream was started

      • canConsumeLong

        public boolean canConsumeLong(LongConsumer consumer) throws IllegalStateException
        Attempt to consume this current token if it can be parsed as a long, and return whether this method was indeed able to consume the token.
        Parameters:
        consumer - the function that should be called with the long value if the current token token could be parsed
        Returns:
        true if the current token did match and was consumed, or false if the current token did not match and therefore was not consumed
        Throws:
        IllegalStateException - if this method was called before the stream was started

      • canConsume

        public boolean canConsume(String expected) throws IllegalStateException
        Attempt to consume this current token if it matches the expected value, and return whether this method was indeed able to consume the token.

        The ANY_VALUE constant can be used in the expected value as a wildcard.

        Parameters:
        expected - the expected value of the current token
        Returns:
        true if the current token did match and was consumed, or false if the current token did not match and therefore was not consumed
        Throws:
        IllegalStateException - if this method was called before the stream was started

      • canConsume

        public boolean canConsume(int type, String expected) throws IllegalStateException
        Attempt to consume this current token if it matches the expected value, and return whether this method was indeed able to consume the token.

        The ANY_VALUE constant can be used in the expected value as a wildcard.

        Parameters:
        type - the expected type of the current token
        expected - the expected value of the current token
        Returns:
        true if the current token did match and was consumed, or false if the current token did not match and therefore was not consumed
        Throws:
        IllegalStateException - if this method was called before the stream was started

      • canConsumeWord

        public boolean canConsumeWord(String expected) throws IllegalStateException
        Attempt to consume this current token if it is TokenStream.BasicTokenizer.WORD and it matches the expected value, and return whether this method was indeed able to consume the token.

        The ANY_VALUE constant can be used in the expected value as a wildcard.

        Parameters:
        expected - the expected value of the current token
        Returns:
        true if the current token did match and was consumed, or false if the current token did not match and therefore was not consumed
        Throws:
        IllegalStateException - if this method was called before the stream was started

      • canConsume

        public boolean canConsume(char expected) throws IllegalStateException
        Attempt to consume this current token if it matches the expected value, and return whether this method was indeed able to consume the token.
        Parameters:
        expected - the expected value of the current token token
        Returns:
        true if the current token did match and was consumed, or false if the current token did not match and therefore was not consumed
        Throws:
        IllegalStateException - if this method was called before the stream was started

      • canConsume

        public boolean canConsume(int expectedType) throws IllegalStateException
        Attempt to consume this current token if it matches the expected token type, and return whether this method was indeed able to consume the token.

        The ANY_TYPE constant can be used in the expected type as a wildcard.

        Parameters:
        expectedType - the expected token type of the current token
        Returns:
        true if the current token did match and was consumed, or false if the current token did not match and therefore was not consumed
        Throws:
        IllegalStateException - if this method was called before the stream was started

      • canConsume

        public boolean canConsume(String currentExpected, String... expectedForNextTokens) throws IllegalStateException
        Attempt to consume this current token and the next tokens if and only if they match the expected values, and return whether this method was indeed able to consume all of the supplied tokens.

        This is not the same as calling canConsume(String) for each of the supplied arguments, since this method ensures that all of the supplied values can be consumed.

        This method is equivalent to calling the following: 

        
 if (tokens.matches(currentExpected, expectedForNextTokens)) {
     tokens.consume(currentExpected, expectedForNextTokens);
 }

        The ANY_VALUE constant can be used in the expected values as a wildcard.

        Parameters:
        currentExpected - the expected value of the current token
        expectedForNextTokens - the expected values fo the following tokens
        Returns:
        true if the current token did match and was consumed, or false if the current token did not match and therefore was not consumed
        Throws:
        IllegalStateException - if this method was called before the stream was started

      • canConsume

        public boolean canConsume(int type, String currentExpected, String... expectedForNextTokens) throws IllegalStateException
        Attempt to consume this current token and the next tokens if and only if they match the expected type and values, and return whether this method was indeed able to consume all of the supplied tokens.

        This is not the same as calling canConsume(type String) for each of the supplied arguments, since this method ensures that all of the supplied values can be consumed.

        This method is equivalent to calling the following: 

        
 if (tokens.matches(currentExpected, expectedForNextTokens) && tokens.matches(type, type, ...)) {
     tokens.consume(currentExpected, expectedForNextTokens);
 }

        The ANY_VALUE constant can be used in the expected values as a wildcard.

        Parameters:
        type - the expect type of the tokens
        currentExpected - the expected value of the current token
        expectedForNextTokens - the expected values fo the following tokens
        Returns:
        true if the current token did match and was consumed, or false if the current token did not match and therefore was not consumed
        Throws:
        IllegalStateException - if this method was called before the stream was started

      • canConsumeWords

        public boolean canConsumeWords(String currentExpected, String... expectedForNextTokens) throws IllegalStateException
        Attempt to consume this current token and the next tokens if and only if they are of TokenStream.BasicTokenizer.WORD and match the expected values, and return whether this method was indeed able to consume all of the supplied tokens.
        Parameters:
        currentExpected - the expected value of the current token
        expectedForNextTokens - the expected values fo the following tokens
        Returns:
        true if the current token did match and was consumed, or false if the current token did not match and therefore was not consumed
        Throws:
        IllegalStateException - if this method was called before the stream was started
        See Also:

      • canConsume

        public boolean canConsume(String[] nextTokens) throws IllegalStateException
        Attempt to consume this current token and the next tokens if and only if they match the expected values, and return whether this method was indeed able to consume all of the supplied tokens.

        This is not the same as calling canConsume(String) for each of the supplied arguments, since this method ensures that all of the supplied values can be consumed.

        This method is equivalent to calling the following: 

        
 if (tokens.matches(currentExpected, expectedForNextTokens)) {
     tokens.consume(currentExpected, expectedForNextTokens);
 }

        The ANY_VALUE constant can be used in the expected values as a wildcard.

        Parameters:
        nextTokens - the expected values of the next tokens
        Returns:
        true if the current token did match and was consumed, or false if the current token did not match and therefore was not consumed
        Throws:
        IllegalStateException - if this method was called before the stream was started

      • canConsume

        public boolean canConsume(Iterable<String> nextTokens) throws IllegalStateException
        Attempt to consume this current token and the next tokens if and only if they match the expected values, and return whether this method was indeed able to consume all of the supplied tokens.

        This is not the same as calling canConsume(String) for each of the supplied arguments, since this method ensures that all of the supplied values can be consumed.

        This method is equivalent to calling the following: 

        
 if (tokens.matches(currentExpected, expectedForNextTokens)) {
     tokens.consume(currentExpected, expectedForNextTokens);
 }

        The ANY_VALUE constant can be used in the expected values as a wildcard.

        Parameters:
        nextTokens - the expected values of the next tokens
        Returns:
        true if the current token did match and was consumed, or false if the current token did not match and therefore was not consumed
        Throws:
        IllegalStateException - if this method was called before the stream was started

      • canConsumeAnyOf

        public boolean canConsumeAnyOf(String firstOption, String... additionalOptions) throws IllegalStateException
        Attempt to consume the next token if it matches one of the supplied values.
        Parameters:
        firstOption - the first option for the value of the current token
        additionalOptions - the additional options for the value of the current token
        Returns:
        true if the current token's value did match one of the supplied options, or false otherwise
        Throws:
        IllegalStateException - if this method was called before the stream was started

      • canConsumeAnyOf

        public boolean canConsumeAnyOf(String[] options) throws IllegalStateException
        Attempt to consume the next token if it matches one of the supplied values.
        Parameters:
        options - the options for the value of the current token
        Returns:
        true if the current token's value did match one of the suplied options, or false otherwise
        Throws:
        IllegalStateException - if this method was called before the stream was started

      • canConsumeAnyOf

        public boolean canConsumeAnyOf(Iterable<String> options) throws IllegalStateException
        Attempt to consume the next token if it matches one of the supplied values.
        Parameters:
        options - the options for the value of the current token
        Returns:
        true if the current token's value did match one of the supplied options, or false otherwise
        Throws:
        IllegalStateException - if this method was called before the stream was started

      • canConsumeAnyOf

        public boolean canConsumeAnyOf(int firstTypeOption, int... additionalTypeOptions) throws IllegalStateException
        Attempt to consume the next token if it matches one of the supplied types.
        Parameters:
        firstTypeOption - the first option for the type of the current token
        additionalTypeOptions - the additional options for the type of the current token
        Returns:
        true if the current token's type matched one of the supplied options, or false otherwise
        Throws:
        IllegalStateException - if this method was called before the stream was started

      • canConsumeAnyOf

        public boolean canConsumeAnyOf(int[] typeOptions) throws IllegalStateException
        Attempt to consume the next token if it matches one of the supplied types.
        Parameters:
        typeOptions - the options for the type of the current token
        Returns:
        true if the current token's type matched one of the supplied options, or false otherwise
        Throws:
        IllegalStateException - if this method was called before the stream was started

      • matches

        public boolean matches(String expected) throws IllegalStateException
        Determine if the current token matches the expected value.

        The ANY_VALUE constant can be used as a wildcard.

        Parameters:
        expected - the expected value of the current token
        Returns:
        true if the current token did match, or false if the current token did not match
        Throws:
        IllegalStateException - if this method was called before the stream was started

      • matches

        public boolean matches(int type, String expected) throws IllegalStateException
        Determine if the current token matches the expected type and a value.

        The ANY_VALUE constant can be used as a wildcard.

        Parameters:
        type - the expected type of the curent token
        expected - the expected value of the current token
        Returns:
        true if the current token did match, or false if the current token did not match
        Throws:
        IllegalStateException - if this method was called before the stream was started

      • matchesWord

        public boolean matchesWord(String expected) throws IllegalStateException
        Determine if the current token is TokenStream.BasicTokenizer.WORD and matches the expected value.

        The ANY_VALUE constant can be used as a wildcard.

        Parameters:
        expected - the expected value of the current token
        Returns:
        true if the current token did match, or false if the current token did not match
        Throws:
        IllegalStateException - if this method was called before the stream was started

      • matches

        public boolean matches(char expected) throws IllegalStateException
        Determine if the current token matches the expected value.
        Parameters:
        expected - the expected value of the current token token
        Returns:
        true if the current token did match, or false if the current token did not match
        Throws:
        IllegalStateException - if this method was called before the stream was started

      • matches

        public boolean matches(int expectedType) throws IllegalStateException
        Determine if the current token matches the expected token type.
        Parameters:
        expectedType - the expected token type of the current token
        Returns:
        true if the current token did match, or false if the current token did not match
        Throws:
        IllegalStateException - if this method was called before the stream was started

      • matches

        public boolean matches(String currentExpected, String... expectedForNextTokens) throws IllegalStateException
        Determine if the next few tokens match the expected values.

        The ANY_VALUE constant can be used in the expected values as a wildcard.

        Parameters:
        currentExpected - the expected value of the current token
        expectedForNextTokens - the expected values for the following tokens
        Returns:
        true if the tokens did match, or false otherwise
        Throws:
        IllegalStateException - if this method was called before the stream was started

      • matches

        public boolean matches(String[] nextTokens) throws IllegalStateException
        Determine if the next few tokens match the expected values.

        The ANY_VALUE constant can be used in the expected values as a wildcard.

        Parameters:
        nextTokens - the expected value of the next tokens
        Returns:
        true if the tokens did match, or false otherwise
        Throws:
        IllegalStateException - if this method was called before the stream was started

      • matches

        public boolean matches(Iterable<String> nextTokens) throws IllegalStateException
        Determine if the next few tokens match the expected values.

        The ANY_VALUE constant can be used in the expected values as a wildcard.

        Parameters:
        nextTokens - the expected value of the next tokens
        Returns:
        true if the tokens did match, or false otherwise
        Throws:
        IllegalStateException - if this method was called before the stream was started

      • matches

        public boolean matches(int currentExpectedType, int... expectedTypeForNextTokens) throws IllegalStateException
        Determine if the next few tokens have the supplied types.

        The ANY_TYPE constant can be used in the expected values as a wildcard.

        Parameters:
        currentExpectedType - the expected type of the current token
        expectedTypeForNextTokens - the expected type for the following tokens
        Returns:
        true if the tokens did match, or false otherwise
        Throws:
        IllegalStateException - if this method was called before the stream was started

      • matches

        public boolean matches(int[] typesForNextTokens) throws IllegalStateException
        Determine if the next few tokens have the supplied types.

        The ANY_TYPE constant can be used in the expected values as a wildcard.

        Parameters:
        typesForNextTokens - the expected type for each of the next tokens
        Returns:
        true if the tokens did match, or false otherwise
        Throws:
        IllegalStateException - if this method was called before the stream was started

      • matchesAnyOf

        public boolean matchesAnyOf(String firstOption, String... additionalOptions) throws IllegalStateException
        Determine if the next token matches one of the supplied values.
        Parameters:
        firstOption - the first option for the value of the current token
        additionalOptions - the additional options for the value of the current token
        Returns:
        true if the current token's value did match one of the supplied options, or false otherwise
        Throws:
        IllegalStateException - if this method was called before the stream was started

      • matchesAnyOf

        public boolean matchesAnyOf(int type, String firstOption, String... additionalOptions) throws IllegalStateException
        Determine if the next token matches one of the supplied values of the expected type.
        Parameters:
        type - the expected type of tokens
        firstOption - the first option for the value of the current token
        additionalOptions - the additional options for the value of the current token
        Returns:
        true if the current token's value did match one of the supplied options, or false otherwise
        Throws:
        IllegalStateException - if this method was called before the stream was started

      • matchesAnyWordOf

        public boolean matchesAnyWordOf(String firstOption, String... additionalOptions) throws IllegalStateException
        Determine if the next token matches one of the supplied values of the type TokenStream.BasicTokenizer.WORD
        Parameters:
        firstOption - the first option for the value of the current token
        additionalOptions - the additional options for the value of the current token
        Returns:
        true if the current token's value did match one of the supplied options, or false otherwise
        Throws:
        IllegalStateException - if this method was called before the stream was started

      • matchesAnyOf

        public boolean matchesAnyOf(String[] options) throws IllegalStateException
        Determine if the next token matches one of the supplied values.
        Parameters:
        options - the options for the value of the current token
        Returns:
        true if the current token's value did match one of the supplied options, or false otherwise
        Throws:
        IllegalStateException - if this method was called before the stream was started

      • matchesAnyOf

        public boolean matchesAnyOf(Iterable<String> options) throws IllegalStateException
        Determine if the next token matches one of the supplied values.
        Parameters:
        options - the options for the value of the current token
        Returns:
        true if the current token's value did match one of the supplied options, or false otherwise
        Throws:
        IllegalStateException - if this method was called before the stream was started

      • matchesAnyOf

        public boolean matchesAnyOf(int firstTypeOption, int... additionalTypeOptions) throws IllegalStateException
        Determine if the next token have one of the supplied types.
        Parameters:
        firstTypeOption - the first option for the type of the current token
        additionalTypeOptions - the additional options for the type of the current token
        Returns:
        true if the current token's type matched one of the supplied options, or false otherwise
        Throws:
        IllegalStateException - if this method was called before the stream was started

      • matchesAnyOf

        public boolean matchesAnyOf(int[] typeOptions) throws IllegalStateException
        Determine if the next token have one of the supplied types.
        Parameters:
        typeOptions - the options for the type of the current token
        Returns:
        true if the current token's type matched one of the supplied options, or false otherwise
        Throws:
        IllegalStateException - if this method was called before the stream was started

      • hasNext

        public boolean hasNext()
        Determine if this stream has another token to be consumed.
        Returns:
        true if there is another token ready for consumption, or false otherwise
        Throws:
        IllegalStateException - if this method was called before the stream was started

      • toString

        public String toString()
        Overrides:
        toString in class Object

      • moveToNextToken

        private void moveToNextToken(List<TokenStream.Token> newTokens)

      • moveToNextToken

        private void moveToNextToken()

      • currentToken

        final TokenStream.Token currentToken() throws IllegalStateException, NoSuchElementException
        Get the current token.
        Returns:
        the current token; never null
        Throws:
        IllegalStateException - if this method was called before the stream was started
        NoSuchElementException - if there are no more tokens

      • getContentFrom

        public String getContentFrom(TokenStream.Marker starting)
        Gets the content string starting at the specified marker (inclusive) and continuing up to the next position (exclusive).
        Parameters:
        starting - the marker describing a point in the stream; may not be null
        Returns:
        the content string; never null

      • getContentBetween

        public String getContentBetween(TokenStream.Marker starting, Position end)
        Gets the content string starting at the specified marker (inclusive) and continuing up to the end position (exclusive).
        Parameters:
        starting - the marker describing a point in the stream; may not be null
        end - the position located directly after the returned content string; can be null, which means end of content
        Returns:
        the content string; never null

      • getContentBetween

        public String getContentBetween(Position starting, Position end)
        Gets the content string starting at the first position (inclusive) and continuing up to the end position (exclusive).
        Parameters:
        starting - the position marking the beginning of the desired content string; may not be null
        end - the position located directly after the returned content string; can be null, which means end of content
        Returns:
        the content string; never null

      • getContentBetween

        protected String getContentBetween(int startIndex, Position end)

      • previousToken

        public final TokenStream.Token previousToken(int count) throws IllegalStateException, NoSuchElementException
        Get the previous token. This does not modify the state.
        Parameters:
        count - the number of tokens back from the current position that this method should return
        Returns:
        the previous token; never null
        Throws:
        IllegalStateException - if this method was called before the stream was started
        NoSuchElementException - if there is no previous token

      • generateFragment

        String generateFragment()

      • generateFragment

        static String generateFragment(String content, int indexOfProblem, int charactersToIncludeBeforeAndAfter, String highlightText)
        Utility method to generate a highlighted fragment of a particular point in the stream.
        Parameters:
        content - the content from which the fragment should be taken; may not be null
        indexOfProblem - the index of the problem point that should be highlighted; must be a valid index in the content
        charactersToIncludeBeforeAndAfter - the maximum number of characters before and after the problem point to include in the fragment
        highlightText - the text that should be included in the fragment at the problem point to highlight the location, or an empty string if there should be no highlighting
        Returns:
        the highlighted fragment; never null

      • basicTokenizer

        public static TokenStream.BasicTokenizer basicTokenizer(boolean includeComments)
        Obtain a basic TokenStream.Tokenizer implementation that ignores whitespace but includes tokens for individual symbols, the period ('.'), single-quoted strings, double-quoted strings, whitespace-delimited words, and optionally comments.

        Note that the resulting Tokenizer may not be appropriate in many situations, but is provided merely as a convenience for those situations that happen to be able to use it.

        Parameters:
        includeComments - true if the comments should be retained and be included in the token stream, or false if comments should be stripped and not included in the token stream
        Returns:
        the tokenizer; never null

      • getInputString

        public String getInputString()
        Returns:
        a string to be parsed