public class

PredicateUtils

extends Object
java.lang.Object
   ↳ org.apache.commons.collections.PredicateUtils

Class Overview

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.

Summary

Public Constructors
PredicateUtils()
This class is not normally instantiated.
Public Methods
static Predicate allPredicate(Collection predicates)
Create a new Predicate that returns true only if all of the specified predicates are true.
static Predicate allPredicate(Predicate[] predicates)
Create a new Predicate that returns true only if all of the specified predicates are true.
static Predicate andPredicate(Predicate predicate1, Predicate predicate2)
Create a new Predicate that returns true only if both of the specified predicates are true.
static Predicate anyPredicate(Predicate[] predicates)
Create a new Predicate that returns true if any of the specified predicates are true.
static Predicate anyPredicate(Collection predicates)
Create a new Predicate that returns true if any of the specified predicates are true.
static Predicate asPredicate(Transformer transformer)
Create a new Predicate that wraps a Transformer.
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.
static Predicate equalPredicate(Object value)
Creates a Predicate that checks if the input object is equal to the specified object using equals().
static Predicate exceptionPredicate()
Gets a Predicate that always throws an exception.
static Predicate falsePredicate()
Gets a Predicate that always returns false.
static Predicate identityPredicate(Object value)
Creates a Predicate that checks if the input object is equal to the specified object by identity.
static Predicate instanceofPredicate(Class type)
Creates a Predicate that checks if the object passed in is of a particular type, using instanceof.
static Predicate invokerPredicate(String methodName)
Creates a Predicate that invokes a method on the input object.
static Predicate invokerPredicate(String methodName, Class[] paramTypes, Object[] args)
Creates a Predicate that invokes a method on the input object.
static Predicate neitherPredicate(Predicate predicate1, Predicate predicate2)
Create a new Predicate that returns true if neither of the specified predicates are true.
static Predicate nonePredicate(Collection predicates)
Create a new Predicate that returns true if none of the specified predicates are true.
static Predicate nonePredicate(Predicate[] predicates)
Create a new Predicate that returns true if none of the specified predicates are true.
static Predicate notNullPredicate()
Gets a Predicate that checks if the input object passed in is not null.
static Predicate notPredicate(Predicate predicate)
Create a new Predicate that returns true if the specified predicate returns false and vice versa.
static Predicate nullIsExceptionPredicate(Predicate predicate)
Gets a Predicate that throws an exception if the input object is null, otherwise it calls the specified Predicate.
static Predicate nullIsFalsePredicate(Predicate predicate)
Gets a Predicate that returns false if the input object is null, otherwise it calls the specified Predicate.
static Predicate nullIsTruePredicate(Predicate predicate)
Gets a Predicate that returns true if the input object is null, otherwise it calls the specified Predicate.
static Predicate nullPredicate()
Gets a Predicate that checks if the input object passed in is null.
static Predicate onePredicate(Collection predicates)
Create a new Predicate that returns true if only one of the specified predicates are true.
static Predicate onePredicate(Predicate[] predicates)
Create a new Predicate that returns true if only one of the specified predicates are true.
static Predicate orPredicate(Predicate predicate1, Predicate predicate2)
Create a new Predicate that returns true if either of the specified predicates are true.
static Predicate transformedPredicate(Transformer transformer, Predicate predicate)
Creates a predicate that transforms the input object before passing it to the predicate.
static Predicate truePredicate()
Gets a Predicate that always returns true.
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.
[Expand]
Inherited Methods
From class java.lang.Object

Public Constructors

public PredicateUtils ()

This class is not normally instantiated.

Public Methods

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

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

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

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

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

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

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

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

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

public static Predicate falsePredicate ()

Gets a Predicate that always returns false.

Returns
  • the predicate
See Also

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

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

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

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

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

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

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

public static Predicate notNullPredicate ()

Gets a Predicate that checks if the input object passed in is not null.

Returns
  • the predicate
See Also

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

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

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

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

public static Predicate nullPredicate ()

Gets a Predicate that checks if the input object passed in is null.

Returns
  • the predicate
See Also

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

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

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

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
See Also

public static Predicate truePredicate ()

Gets a Predicate that always returns true.

Returns
  • the predicate
See Also

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