Package org.apache.commons.collections4

Class PredicateUtils

java.lang.Object
org.apache.commons.collections4.PredicateUtils
public class PredicateUtils extends Object
PredicateUtils provides reference implementations and utilities for the Predicate functor interface. The supplied predicates are:
  • Invoker - returns the result of a method call on the input object
  • InstanceOf - true if the object is an instanceof a class
  • Equal - true if the object equals() a specified object
  • Identity - true if the object == a specified object
  • Null - true if the object is null
  • NotNull - true if the object is not null
  • Unique - true if the object has not already been evaluated
  • And/All - true if all of the predicates are true
  • Or/Any - true if any of the predicates is true
  • Either/One - true if only one of the predicate is true
  • Neither/None - true if none of the predicates are true
  • Not - true if the predicate is false, and vice versa
  • Transformer - wraps a Transformer as a Predicate
  • True - always return true
  • False - always return false
  • Exception - always throws an exception
  • NullIsException/NullIsFalse/NullIsTrue - check for null input
  • Transformed - transforms the input before calling the predicate

All the supplied predicates are Serializable.

Since:
3.0

  • Method Details

    • allPredicate

      public static <T> Predicate<T> allPredicate(Collection<? extends Predicate<? super T>> predicates)
      Creates a new Predicate that returns true only if all of the specified predicates are true. The predicates are checked in iterator order. If the collection of predicates is empty, then this predicate returns true.
      Type Parameters:
      T - the type that the predicate queries.
      Parameters:
      predicates - A collection of predicates to check, may not be null.
      Returns:
      The all predicate.
      Throws:
      NullPointerException - if the predicates collection is null.
      NullPointerException - if any predicate in the collection is null.
      See Also:

    • allPredicate

      public static <T> Predicate<T> allPredicate(Predicate<? super T>... predicates)
      Creates a new Predicate that returns true only if all of the specified predicates are true. If the array of predicates is empty, then this predicate returns true.
      Type Parameters:
      T - the type that the predicate queries.
      Parameters:
      predicates - An array of predicates to check, may not be null.
      Returns:
      The all predicate.
      Throws:
      NullPointerException - if the predicates array is null.
      NullPointerException - if any predicate in the array is null.
      See Also:

    • andPredicate

      public static <T> Predicate<T> andPredicate(Predicate<? super T> predicate1, Predicate<? super T> predicate2)
      Creates a new Predicate that returns true only if both of the specified predicates are true.
      Type Parameters:
      T - the type that the predicate queries.
      Parameters:
      predicate1 - The first predicate, may not be null.
      predicate2 - The second predicate, may not be null.
      Returns:
      The and predicate.
      Throws:
      NullPointerException - if either predicate is null.
      See Also:

    • anyPredicate

      public static <T> Predicate<T> anyPredicate(Collection<? extends Predicate<? super T>> predicates)
      Creates a new Predicate that returns true if any of the specified predicates are true. The predicates are checked in iterator order. If the collection of predicates is empty, then this predicate returns false.
      Type Parameters:
      T - the type that the predicate queries.
      Parameters:
      predicates - A collection of predicates to check, may not be null.
      Returns:
      The any predicate.
      Throws:
      NullPointerException - if the predicates collection is null.
      NullPointerException - if any predicate in the collection is null.
      See Also:

    • anyPredicate

      public static <T> Predicate<T> anyPredicate(Predicate<? super T>... predicates)
      Creates a new Predicate that returns true if any of the specified predicates are true. If the array of predicates is empty, then this predicate returns false.
      Type Parameters:
      T - the type that the predicate queries.
      Parameters:
      predicates - An array of predicates to check, may not be null.
      Returns:
      The any predicate.
      Throws:
      NullPointerException - if the predicates array is null.
      NullPointerException - if any predicate in the array is null.
      See Also:

    • asPredicate

      public static <T> Predicate<T> asPredicate(Transformer<? super T,Boolean> transformer)
      Creates a new Predicate that wraps a Transformer. The Transformer must return either Boolean.TRUE or Boolean.FALSE otherwise a PredicateException will be thrown.
      Type Parameters:
      T - the type that the predicate queries.
      Parameters:
      transformer - The transformer to wrap, may not be null.
      Returns:
      The transformer wrapping predicate.
      Throws:
      NullPointerException - if the transformer is null.
      See Also:

    • eitherPredicate

      public static <T> Predicate<T> eitherPredicate(Predicate<? super T> predicate1, Predicate<? super T> predicate2)
      Creates a new Predicate that returns true if one, but not both, of the specified predicates are true. XOR
      Type Parameters:
      T - the type that the predicate queries.
      Parameters:
      predicate1 - The first predicate, may not be null.
      predicate2 - The second predicate, may not be null.
      Returns:
      The either predicate.
      Throws:
      NullPointerException - if either predicate is null.
      See Also:

    • equalPredicate

      public static <T> Predicate<T> equalPredicate(T value)
      Creates a Predicate that checks if the input object is equal to the specified object using equals().
      Type Parameters:
      T - the type that the predicate queries.
      Parameters:
      value - The value to compare against.
      Returns:
      The predicate.
      See Also:

    • exceptionPredicate

      public static <T> Predicate<T> exceptionPredicate()
      Gets a Predicate that always throws an exception. This could be useful during testing as a placeholder.
      Type Parameters:
      T - the type that the predicate queries.
      Returns:
      The predicate.
      See Also:

    • falsePredicate

      public static <T> Predicate<T> falsePredicate()
      Gets a Predicate that always returns false.
      Type Parameters:
      T - the type that the predicate queries.
      Returns:
      The predicate.
      See Also:

    • identityPredicate

      public static <T> Predicate<T> identityPredicate(T value)
      Creates a Predicate that checks if the input object is equal to the specified object by identity.
      Type Parameters:
      T - the type that the predicate queries.
      Parameters:
      value - The value to compare against.
      Returns:
      The predicate.
      See Also:

    • instanceofPredicate

      public static Predicate<Object> instanceofPredicate(Class<?> type)
      Creates a Predicate that checks if the object passed in is of a particular type, using instanceof. A null input object will return false.
      Parameters:
      type - The type to check for, may not be null.
      Returns:
      The predicate.
      Throws:
      NullPointerException - if the class is null.
      See Also:

    • invokerPredicate

      public static <T> Predicate<T> invokerPredicate(String methodName)
      Creates a Predicate that invokes a method on the input object. The method must return either a boolean or a non-null Boolean, and have no parameters. If the input object is null, a PredicateException is thrown.

      For ePredicateUtils.invokerPredicate("isEmpty");} will call the isEmpty method on the input object to determine the predicate result.

      Type Parameters:
      T - the type that the predicate queries.
      Parameters:
      methodName - The method name to call on the input object, may not be null.
      Returns:
      The predicate.
      Throws:
      NullPointerException - if the methodName is null.
      See Also:

    • invokerPredicate

      public static <T> Predicate<T> invokerPredicate(String methodName, Class<?>[] paramTypes, Object[] args)
      Creates a Predicate that invokes a method on the input object. The method must return either a boolean or a non-null Boolean, and have no parameters. If the input object is null, a PredicateException is thrown.

      For example, PredicateUtils.invokerPredicate("isEmpty"); will call the isEmpty method on the input object to determine the predicate result.

      Type Parameters:
      T - the type that the predicate queries.
      Parameters:
      methodName - The method name to call on the input object, may not be null.
      paramTypes - The parameter types.
      args - The arguments.
      Returns:
      The predicate.
      Throws:
      NullPointerException - if the method name is null.
      IllegalArgumentException - if the paramTypes and args don't match.
      See Also:

    • neitherPredicate

      public static <T> Predicate<T> neitherPredicate(Predicate<? super T> predicate1, Predicate<? super T> predicate2)
      Creates a new Predicate that returns true if neither of the specified predicates are true.
      Type Parameters:
      T - the type that the predicate queries.
      Parameters:
      predicate1 - The first predicate, may not be null.
      predicate2 - The second predicate, may not be null.
      Returns:
      The neither predicate.
      Throws:
      NullPointerException - if either predicate is null.
      See Also:

    • nonePredicate

      public static <T> Predicate<T> nonePredicate(Collection<? extends Predicate<? super T>> predicates)
      Creates a new Predicate that returns true if none of the specified predicates are true. The predicates are checked in iterator order. If the collection of predicates is empty, then this predicate returns true.
      Type Parameters:
      T - the type that the predicate queries.
      Parameters:
      predicates - A collection of predicates to check, may not be null.
      Returns:
      The none predicate.
      Throws:
      NullPointerException - if the predicates collection is null.
      NullPointerException - if any predicate in the collection is null.
      See Also:

    • nonePredicate

      public static <T> Predicate<T> nonePredicate(Predicate<? super T>... predicates)
      Creates a new Predicate that returns true if none of the specified predicates are true. If the array of predicates is empty, then this predicate returns true.
      Type Parameters:
      T - the type that the predicate queries.
      Parameters:
      predicates - An array of predicates to check, may not be null.
      Returns:
      The none predicate.
      Throws:
      NullPointerException - if the predicates array is null.
      NullPointerException - if any predicate in the array is null.
      See Also:

    • notNullPredicate

      public static <T> Predicate<T> notNullPredicate()
      Gets a Predicate that checks if the input object passed in is not null.
      Type Parameters:
      T - the type that the predicate queries.
      Returns:
      The predicate.
      See Also:

    • notPredicate

      public static <T> Predicate<T> notPredicate(Predicate<? super T> predicate)
      Creates a new Predicate that returns true if the specified predicate returns false and vice versa.
      Type Parameters:
      T - the type that the predicate queries.
      Parameters:
      predicate - The predicate to not.
      Returns:
      The not predicate.
      Throws:
      NullPointerException - if the predicate is null.
      See Also:

    • nullIsExceptionPredicate

      public static <T> Predicate<T> nullIsExceptionPredicate(Predicate<? super T> predicate)
      Gets a Predicate that throws an exception if the input object is null, otherwise it calls the specified Predicate. This allows null handling behavior to be added to Predicates that don't support nulls.
      Type Parameters:
      T - the type that the predicate queries.
      Parameters:
      predicate - The predicate to wrap, may not be null.
      Returns:
      A new predicate that throws a NullPointerException if the input is null, otherwise delegates to the given predicate.
      Throws:
      NullPointerException - if the predicate is null.
      See Also:

    • nullIsFalsePredicate

      public static <T> Predicate<T> nullIsFalsePredicate(Predicate<? super T> predicate)
      Gets a Predicate that returns false if the input object is null, otherwise it calls the specified Predicate. This allows null handling behavior to be added to Predicates that don't support nulls.
      Type Parameters:
      T - the type that the predicate queries.
      Parameters:
      predicate - The predicate to wrap, may not be null.
      Returns:
      A new predicate that returns false if the input is null, otherwise delegates to the given predicate.
      Throws:
      NullPointerException - if the predicate is null.
      See Also:

    • nullIsTruePredicate

      public static <T> Predicate<T> nullIsTruePredicate(Predicate<? super T> predicate)
      Gets a Predicate that returns true if the input object is null, otherwise it calls the specified Predicate. This allows null handling behavior to be added to Predicates that don't support nulls.
      Type Parameters:
      T - the type that the predicate queries.
      Parameters:
      predicate - The predicate to wrap, may not be null.
      Returns:
      A new predicate that returns true if the input is null, otherwise delegates to the given predicate.
      Throws:
      NullPointerException - if the predicate is null.
      See Also:

    • nullPredicate

      public static <T> Predicate<T> nullPredicate()
      Gets a Predicate that checks if the input object passed in is null.
      Type Parameters:
      T - the type that the predicate queries.
      Returns:
      The predicate.
      See Also:

    • onePredicate

      public static <T> Predicate<T> onePredicate(Collection<? extends Predicate<? super T>> predicates)
      Creates a new Predicate that returns true if only one of the specified predicates are true. The predicates are checked in iterator order. If the collection of predicates is empty, then this predicate returns false.
      Type Parameters:
      T - the type that the predicate queries.
      Parameters:
      predicates - A collection of predicates to check, may not be null.
      Returns:
      The one predicate.
      Throws:
      NullPointerException - if the predicates collection is null.
      NullPointerException - if any predicate in the collection is null.
      See Also:

    • onePredicate

      public static <T> Predicate<T> onePredicate(Predicate<? super T>... predicates)
      Creates a new Predicate that returns true if only one of the specified predicates are true. If the array of predicates is empty, then this predicate returns false.
      Type Parameters:
      T - the type that the predicate queries.
      Parameters:
      predicates - An array of predicates to check, may not be null.
      Returns:
      The one predicate.
      Throws:
      NullPointerException - if the predicates array is null.
      NullPointerException - if any predicate in the array is null.
      See Also:

    • orPredicate

      public static <T> Predicate<T> orPredicate(Predicate<? super T> predicate1, Predicate<? super T> predicate2)
      Creates a new Predicate that returns true if either of the specified predicates are true.
      Type Parameters:
      T - the type that the predicate queries.
      Parameters:
      predicate1 - The first predicate, may not be null.
      predicate2 - The second predicate, may not be null.
      Returns:
      The or predicate.
      Throws:
      NullPointerException - if either predicate is null.
      See Also:

    • transformedPredicate

      public static <T> Predicate<T> transformedPredicate(Transformer<? super T,? extends T> transformer, Predicate<? super T> predicate)
      Creates a predicate that transforms the input object before passing it to the predicate.
      Type Parameters:
      T - the type that the predicate queries.
      Parameters:
      transformer - The transformer to call first.
      predicate - The predicate to call with the result of the transform.
      Returns:
      A new predicate that transforms the input object using the given transformer and then passes the result to the given predicate.
      Throws:
      NullPointerException - if the transformer or the predicate is null.
      Since:
      3.1
      See Also:

    • truePredicate

      public static <T> Predicate<T> truePredicate()
      Gets a Predicate that always returns true.
      Type Parameters:
      T - the type that the predicate queries.
      Returns:
      The predicate.
      See Also:

    • uniquePredicate

      public static <T> Predicate<T> uniquePredicate()
      Creates a Predicate that returns true the first time an object is encountered, and false if the same object is received again. The comparison is by equals(). A null input object is accepted and will return true the first time, and false subsequently as well.
      Type Parameters:
      T - the type that the predicate queries.
      Returns:
      The predicate.
      See Also: