Package nl.vpro.util

Class Helper

java.lang.Object
nl.vpro.util.Helper
public class Helper extends Object
Simple helper methods.
Author:
arne, peter, [email protected]

  • Method Details

    • withDefault

      public static <T> T withDefault(T value, T def)
      Gives a default in case the value is null.
      Type Parameters:
      T - the type of the value
      Parameters:
      value - a value
      def - the default
      Returns:
      value when value is not null, def otherwise
      See Also:

    • withDefault

      public static int withDefault(int value, int def)
      Gives a default in case the value is -1.
      Parameters:
      value - a value
      def - the default
      Returns:
      the value if it is not -1, def otherwise

    • nvl

      @SafeVarargs public static <T> T nvl(T... values)
      Returns the first non-null value. This method is also known as coalesce.
      Type Parameters:
      T - the type of the value
      Parameters:
      values - the values
      Returns:
      the first non-null value in the arguments, or null when values is null or when all given values in it are all null
      See Also:

    • nvl

      public static String nvl(String... values)

    • firstNonNull

      public static <T> T firstNonNull(List<T> values)
      Returns the first non-null value. This method is also known as coalesce.
      Parameters:
      values - the values
      Returns:
      the first non-null value in the arguments, or null when values is null or when all given values in it are all null
      See Also:

    • firstNonNull

      public static <T> T firstNonNull(Set<T> values)
      Returns the first non-null value. This method is also known as coalesce.
      Parameters:
      values - the values
      Returns:
      the first non-null value in the arguments, or null when values is null or when all given values in it are all null
      See Also:

    • add

      public static <K, L extends K, V, W extends V> void add(Map<K,List<V>> listMap, L key, W value)
      Adds a value to a map of lists. A value list is created when there is no entry in the map for the given key.
      Type Parameters:
      K - key type in the map
      L - actual used key type
      V - list type in the map
      W - actual used list type
      Parameters:
      listMap - the map of lists (not null)
      key - the key (may be null when the map supports null keys)
      value - the value to put in the list

    • addToSetMap

      public static <K, L extends K, V, W extends V> void addToSetMap(Map<K,Set<V>> setMap, L key, W value)
      Adds a value to a map of sets. A value set is created when there is no entry in the map for the given key.
      Type Parameters:
      K - key type in the map
      L - actual used key type
      V - set type in the map
      W - actual used set type
      Parameters:
      setMap - the map of sets (not null)
      key - the key (may be null when the map supports null keys)
      value - the value to put in the set

    • putIfNotNull

      public static <K, V> void putIfNotNull(Map<K,V> map, K key, V value)
      Puts a value in a map when the value is not null.
      Type Parameters:
      K - the key type
      V - the value type
      Parameters:
      map - the map (not null)
      key - the key, can be null when the map supports it
      value - the value or null to do nothing

    • isNumber

      public static boolean isNumber(String text)
      Determines whether some string is a number. No range check is performed.
      Parameters:
      text - the string of which must be determined if it's a number
      Returns:
      true if text is a number, false otherwise

    • numberCast

      public static <N extends Number> N numberCast(Number value, Class<N> targetType)
      Converts a number to another number, potentially rounding to fit the target type.

      Does all standard java types except Atomic* and Mutable*.

      Type Parameters:
      N - the target number type
      Parameters:
      value - the number to convert
      targetType - the return type (not null)
      Returns:
      value cast to type N or null when value is null. Note that the information may be discarded when the value is incompatible with the target type.

    • arrayContains

      @SafeVarargs public static <T> boolean arrayContains(T element, T... array)
      Tries and find an element in an array. equals is used for comparisons. A linear search is performed - if the input array is sorted, it would be wiser to use Arrays.binarySearch(Object[], Object).
      Type Parameters:
      T - the array type
      Parameters:
      element - the element to find
      array - the array to search in
      Returns:
      true if the array contains the element, false otherwise

    • compare

      public static int compare(Comparable o1, Comparable o2)
      Compare, taking null into account (null <).
      Parameters:
      o1 - first
      o2 - second
      Returns:
      1,0,-1

    • toSingleton

      public static <T> T toSingleton(List<T> list)
      Convert a singleton list into the singleton element.
      Type Parameters:
      T - The type of the list
      Parameters:
      list - the list
      Returns:
      the singleton in the list, or null if the list is null or the size of the list is zero.
      Throws:
      IllegalStateException - when more than one element is found in the list.

    • toSingleton

      public static <T> T toSingleton(Set<T> set)
      Convert a singleton set into the singleton element.
      Type Parameters:
      T - The type of the set
      Parameters:
      set - the set
      Returns:
      the singleton in the set, or null if the set is null or the size of the set is zero.
      Throws:
      IllegalStateException - when more than one element is found in the set.

    • isAssignableFrom

      public static boolean isAssignableFrom(Object toTest, String name)
      Parameters:
      toTest - The object to test
      name - The FQN of the class to test againts. The class should be in the classpath
      Returns:
      true if the 'name' is assignable from 'toTest'

    • isAssignableFrom

      public static boolean isAssignableFrom(String toTest, String name)
      Parameters:
      toTest - The FQN object to test. The class should be in the classpath
      name - The FQN of the class to test against. The class should be in the classpath
      Returns:
      true if the 'name' is assignable from 'toTest'

    • getClass

      public static <T> Class<T> getClass(String name)

    • getAnnotatedProperty

      public static <W extends Annotation> String getAnnotatedProperty(Class<?> clazz, Class<W> annClazz)

    • removeNullEntries

      public static <T> List<T> removeNullEntries(List<T> source)

    • appendIfNotEmpty

      public static StringBuilder appendIfNotEmpty(StringBuilder sb, String s)

    • join

      public static <T> String join(Collection<T> list, String sep)
      joins all items in the given list using String.valueOf on each item seperated by the sep String
      Parameters:
      list - The list to join
      sep - The separator String
      Returns:
      the result

    • sim

      public static <T extends Comparable<? super T>> List<T> sim(List<T> a, List<T> b)
      Determine the similar elements in both lists. Result will be sorted.
      Parameters:
      a - List a
      b - List b
      Returns:
      The similar elements for both lists

    • spliceNumber

      public static List<String> spliceNumber(Number number, int maxPartSize)
      Will splice the number in chunks no larger then maxPartSize
      Parameters:
      number - The number to splice
      maxPartSize - The maximum size of a part in the path
      Returns:
      A list of the spliced id

    • spliceNumber

      public static List<String> spliceNumber(Number number, int minPartSize, int maxPartSize)
      Will splice the number in chunks no larger then maxPartSize
      Parameters:
      number - The number to splice
      minPartSize - The minimal size of a part, smaller will be skipped
      maxPartSize - The maximum size of a part in the path
      Returns:
      A list of the spliced id