Package com.google.common.base

Class Strings

  • @GwtCompatible
public final class Strings
extends Object
    Static utility methods pertaining to String or CharSequence instances.
    Since:
    3.0

    • Method Summary

      All Methods Static Methods Concrete Methods 
      Modifier and Type Method Description
      static String commonPrefix​(CharSequence a, CharSequence b)
      Returns the longest string prefix such that a.toString().startsWith(prefix) && b.toString().startsWith(prefix), taking care not to split surrogate pairs.
      static String commonSuffix​(CharSequence a, CharSequence b)
      Returns the longest string suffix such that a.toString().endsWith(suffix) && b.toString().endsWith(suffix), taking care not to split surrogate pairs.
      static String emptyToNull​(String string)
      Returns the given string if it is nonempty; null otherwise.
      static boolean isNullOrEmpty​(String string)
      Returns true if the given string is null or is the empty string.
      static String nullToEmpty​(String string)
      Returns the given string if it is non-null; the empty string otherwise.
      static String padEnd​(String string, int minLength, char padChar)
      Returns a string, of length at least minLength, consisting of string appended with as many copies of padChar as are necessary to reach that length.
      static String padStart​(String string, int minLength, char padChar)
      Returns a string, of length at least minLength, consisting of string prepended with as many copies of padChar as are necessary to reach that length.
      static String repeat​(String string, int count)
      Returns a string consisting of a specific number of concatenated copies of an input string.

    • Method Detail

      • nullToEmpty

        public static String nullToEmpty​(@Nullable
                                 String string)
        Returns the given string if it is non-null; the empty string otherwise.
        Parameters:
        string - the string to test and possibly return
        Returns:
        string itself if it is non-null; "" if it is null

      • emptyToNull

        @Nullable
public static String emptyToNull​(@Nullable
                                 String string)
        Returns the given string if it is nonempty; null otherwise.
        Parameters:
        string - the string to test and possibly return
        Returns:
        string itself if it is nonempty; null if it is empty or null

      • isNullOrEmpty

        public static boolean isNullOrEmpty​(@Nullable
                                    String string)
        Returns true if the given string is null or is the empty string.

        Consider normalizing your string references with nullToEmpty(java.lang.String). If you do, you can use String.isEmpty() instead of this method, and you won't need special null-safe forms of methods like String.toUpperCase(java.util.Locale) either. Or, if you'd like to normalize "in the other direction," converting empty strings to null, you can use emptyToNull(java.lang.String).

        Parameters:
        string - a string reference to check
        Returns:
        true if the string is null or is the empty string

      • padStart

        public static String padStart​(String string,
                              int minLength,
                              char padChar)
        Returns a string, of length at least minLength, consisting of string prepended with as many copies of padChar as are necessary to reach that length. For example,
        • padStart("7", 3, '0') returns "007"
        • padStart("2010", 3, '0') returns "2010"

        See Formatter for a richer set of formatting capabilities.

        Parameters:
        string - the string which should appear at the end of the result
        minLength - the minimum length the resulting string must have. Can be zero or negative, in which case the input string is always returned.
        padChar - the character to insert at the beginning of the result until the minimum length is reached
        Returns:
        the padded string

      • padEnd

        public static String padEnd​(String string,
                            int minLength,
                            char padChar)
        Returns a string, of length at least minLength, consisting of string appended with as many copies of padChar as are necessary to reach that length. For example,
        • padEnd("4.", 5, '0') returns "4.000"
        • padEnd("2010", 3, '!') returns "2010"

        See Formatter for a richer set of formatting capabilities.

        Parameters:
        string - the string which should appear at the beginning of the result
        minLength - the minimum length the resulting string must have. Can be zero or negative, in which case the input string is always returned.
        padChar - the character to append to the end of the result until the minimum length is reached
        Returns:
        the padded string

      • repeat

        public static String repeat​(String string,
                            int count)
        Returns a string consisting of a specific number of concatenated copies of an input string. For example, repeat("hey", 3) returns the string "heyheyhey".
        Parameters:
        string - any non-null string
        count - the number of times to repeat it; a nonnegative integer
        Returns:
        a string containing string repeated count times (the empty string if count is zero)
        Throws:
        IllegalArgumentException - if count is negative

      • commonPrefix

        public static String commonPrefix​(CharSequence a,
                                  CharSequence b)
        Returns the longest string prefix such that a.toString().startsWith(prefix) && b.toString().startsWith(prefix), taking care not to split surrogate pairs. If a and b have no common prefix, returns the empty string.
        Since:
        11.0

      • commonSuffix

        public static String commonSuffix​(CharSequence a,
                                  CharSequence b)
        Returns the longest string suffix such that a.toString().endsWith(suffix) && b.toString().endsWith(suffix), taking care not to split surrogate pairs. If a and b have no common suffix, returns the empty string.
        Since:
        11.0