Package org.apache.commons.collections

Class PredicateUtils

java.lang.Object
org.apache.commons.collections.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:
Commons Collections 3.0
Version:
$Revision: 647116 $ $Date: 2008-04-11 13:23:08 +0200 (Fri, 11 Apr 2008) $
Author:
Stephen Colebourne, Ola Berg

  • Constructor Details

    • PredicateUtils

      public PredicateUtils()
      This class is not normally instantiated.

  • Method Details

    • exceptionPredicate

      public static Predicate exceptionPredicate()
      Gets a Predicate that always throws an exception. This could be useful during testing as a placeholder.
      Returns:
      the predicate
      See Also:

    • truePredicate

      public static Predicate truePredicate()
      Gets a Predicate that always returns true.
      Returns:
      the predicate
      See Also:

    • falsePredicate

      public static Predicate falsePredicate()
      Gets a Predicate that always returns false.
      Returns:
      the predicate
      See Also:

    • nullPredicate

      public static Predicate nullPredicate()
      Gets a Predicate that checks if the input object passed in is null.
      Returns:
      the predicate
      See Also:

    • notNullPredicate

      public static Predicate notNullPredicate()
      Gets a Predicate that checks if the input object passed in is not null.
      Returns:
      the predicate
      See Also:

    • equalPredicate

      public static Predicate equalPredicate(Object value)
      Creates a Predicate that checks if the input object is equal to the specified object using equals().
      Parameters:
      value - the value to compare against
      Returns:
      the predicate
      See Also:

    • identityPredicate

      public static Predicate identityPredicate(Object value)
      Creates a Predicate that checks if the input object is equal to the specified object by identity.
      Parameters:
      value - the value to compare against
      Returns:
      the predicate
      See Also:

    • instanceofPredicate

      public static Predicate 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:
      IllegalArgumentException - if the class is null
      See Also:

    • uniquePredicate

      public static Predicate 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.
      Returns:
      the predicate
      See Also:

    • invokerPredicate

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

      Parameters:
      methodName - the method name to call on the input object, may not be null
      Returns:
      the predicate
      Throws:
      IllegalArgumentException - if the methodName is null.
      See Also:

    • invokerPredicate

      public static Predicate 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.

      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:
      IllegalArgumentException - if the method name is null
      IllegalArgumentException - if the paramTypes and args don't match
      See Also:

    • andPredicate

      public static Predicate andPredicate(Predicate predicate1, Predicate predicate2)
      Create a new Predicate that returns true only if both of the specified predicates are true.
      Parameters:
      predicate1 - the first predicate, may not be null
      predicate2 - the second predicate, may not be null
      Returns:
      the and predicate
      Throws:
      IllegalArgumentException - if either predicate is null
      See Also:

    • allPredicate

      public static Predicate allPredicate(Predicate[] predicates)
      Create 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.
      Parameters:
      predicates - an array of predicates to check, may not be null
      Returns:
      the all predicate
      Throws:
      IllegalArgumentException - if the predicates array is null
      IllegalArgumentException - if any predicate in the array is null
      See Also:

    • allPredicate

      public static Predicate allPredicate(Collection predicates)
      Create 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.
      Parameters:
      predicates - a collection of predicates to check, may not be null
      Returns:
      the all predicate
      Throws:
      IllegalArgumentException - if the predicates collection is null
      IllegalArgumentException - if any predicate in the collection is null
      See Also:

    • orPredicate

      public static Predicate orPredicate(Predicate predicate1, Predicate predicate2)
      Create a new Predicate that returns true if either of the specified predicates are true.
      Parameters:
      predicate1 - the first predicate, may not be null
      predicate2 - the second predicate, may not be null
      Returns:
      the or predicate
      Throws:
      IllegalArgumentException - if either predicate is null
      See Also:

    • anyPredicate

      public static Predicate anyPredicate(Predicate[] predicates)
      Create 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.
      Parameters:
      predicates - an array of predicates to check, may not be null
      Returns:
      the any predicate
      Throws:
      IllegalArgumentException - if the predicates array is null
      IllegalArgumentException - if any predicate in the array is null
      See Also:

    • anyPredicate

      public static Predicate anyPredicate(Collection predicates)
      Create 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.
      Parameters:
      predicates - a collection of predicates to check, may not be null
      Returns:
      the any predicate
      Throws:
      IllegalArgumentException - if the predicates collection is null
      IllegalArgumentException - if any predicate in the collection is null
      See Also:

    • eitherPredicate

      public static Predicate eitherPredicate(Predicate predicate1, Predicate predicate2)
      Create a new Predicate that returns true if one, but not both, of the specified predicates are true.
      Parameters:
      predicate1 - the first predicate, may not be null
      predicate2 - the second predicate, may not be null
      Returns:
      the either predicate
      Throws:
      IllegalArgumentException - if either predicate is null
      See Also:

    • onePredicate

      public static Predicate onePredicate(Predicate[] predicates)
      Create 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.
      Parameters:
      predicates - an array of predicates to check, may not be null
      Returns:
      the one predicate
      Throws:
      IllegalArgumentException - if the predicates array is null
      IllegalArgumentException - if any predicate in the array is null
      See Also:

    • onePredicate

      public static Predicate onePredicate(Collection predicates)
      Create 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.
      Parameters:
      predicates - a collection of predicates to check, may not be null
      Returns:
      the one predicate
      Throws:
      IllegalArgumentException - if the predicates collection is null
      IllegalArgumentException - if any predicate in the collection is null
      See Also:

    • neitherPredicate

      public static Predicate neitherPredicate(Predicate predicate1, Predicate predicate2)
      Create a new Predicate that returns true if neither of the specified predicates are true.
      Parameters:
      predicate1 - the first predicate, may not be null
      predicate2 - the second predicate, may not be null
      Returns:
      the neither predicate
      Throws:
      IllegalArgumentException - if either predicate is null
      See Also:

    • nonePredicate

      public static Predicate nonePredicate(Predicate[] predicates)
      Create 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.
      Parameters:
      predicates - an array of predicates to check, may not be null
      Returns:
      the none predicate
      Throws:
      IllegalArgumentException - if the predicates array is null
      IllegalArgumentException - if any predicate in the array is null
      See Also:

    • nonePredicate

      public static Predicate nonePredicate(Collection predicates)
      Create 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.
      Parameters:
      predicates - a collection of predicates to check, may not be null
      Returns:
      the none predicate
      Throws:
      IllegalArgumentException - if the predicates collection is null
      IllegalArgumentException - if any predicate in the collection is null
      See Also:

    • notPredicate

      public static Predicate notPredicate(Predicate predicate)
      Create a new Predicate that returns true if the specified predicate returns false and vice versa.
      Parameters:
      predicate - the predicate to not
      Returns:
      the not predicate
      Throws:
      IllegalArgumentException - if the predicate is null
      See Also:

    • asPredicate

      public static Predicate asPredicate(Transformer transformer)
      Create a new Predicate that wraps a Transformer. The Transformer must return either Boolean.TRUE or Boolean.FALSE otherwise a PredicateException will be thrown.
      Parameters:
      transformer - the transformer to wrap, may not be null
      Returns:
      the transformer wrapping predicate
      Throws:
      IllegalArgumentException - if the transformer is null
      See Also:

    • nullIsExceptionPredicate

      public static Predicate nullIsExceptionPredicate(Predicate predicate)
      Gets a Predicate that throws an exception if the input object is null, otherwise it calls the specified Predicate. This allows null handling behaviour to be added to Predicates that don't support nulls.
      Parameters:
      predicate - the predicate to wrap, may not be null
      Returns:
      the predicate
      Throws:
      IllegalArgumentException - if the predicate is null.
      See Also:

    • nullIsFalsePredicate

      public static Predicate nullIsFalsePredicate(Predicate predicate)
      Gets a Predicate that returns false if the input object is null, otherwise it calls the specified Predicate. This allows null handling behaviour to be added to Predicates that don't support nulls.
      Parameters:
      predicate - the predicate to wrap, may not be null
      Returns:
      the predicate
      Throws:
      IllegalArgumentException - if the predicate is null.
      See Also:

    • nullIsTruePredicate

      public static Predicate nullIsTruePredicate(Predicate predicate)
      Gets a Predicate that returns true if the input object is null, otherwise it calls the specified Predicate. This allows null handling behaviour to be added to Predicates that don't support nulls.
      Parameters:
      predicate - the predicate to wrap, may not be null
      Returns:
      the predicate
      Throws:
      IllegalArgumentException - if the predicate is null.
      See Also:

    • transformedPredicate

      public static Predicate transformedPredicate(Transformer transformer, Predicate predicate)
      Creates a predicate that transforms the input object before passing it to the predicate.
      Parameters:
      transformer - the transformer to call first
      predicate - the predicate to call with the result of the transform
      Returns:
      the predicate
      Throws:
      IllegalArgumentException - if the transformer or the predicate is null
      Since:
      Commons Collections 3.1
      See Also: