Package org.apache.commons.collections
Class PredicateUtils
- java.lang.Object
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- org.apache.commons.collections.PredicateUtils
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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
- 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
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Constructor Summary
Constructors Constructor Description PredicateUtils()
This class is not normally instantiated.
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Method Summary
All Methods Static Methods Concrete Methods Modifier and Type Method Description 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(Collection predicates)
Create a new Predicate that returns true if any 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
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.
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Method Detail
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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:
ExceptionPredicate
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truePredicate
public static Predicate truePredicate()
Gets a Predicate that always returns true.- Returns:
- the predicate
- See Also:
TruePredicate
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falsePredicate
public static Predicate falsePredicate()
Gets a Predicate that always returns false.- Returns:
- the predicate
- See Also:
FalsePredicate
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nullPredicate
public static Predicate nullPredicate()
Gets a Predicate that checks if the input object passed in is null.- Returns:
- the predicate
- See Also:
NullPredicate
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notNullPredicate
public static Predicate notNullPredicate()
Gets a Predicate that checks if the input object passed in is not null.- Returns:
- the predicate
- See Also:
NotNullPredicate
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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:
EqualPredicate
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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:
IdentityPredicate
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instanceofPredicate
public static Predicate instanceofPredicate(Class type)
Creates a Predicate that checks if the object passed in is of a particular type, using instanceof. Anull
input object will returnfalse
.- Parameters:
type
- the type to check for, may not be null- Returns:
- the predicate
- Throws:
IllegalArgumentException
- if the class is null- See Also:
InstanceofPredicate
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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(). Anull
input object is accepted and will return true the first time, and false subsequently as well.- Returns:
- the predicate
- See Also:
UniquePredicate
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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 theisEmpty
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:
InvokerTransformer
,TransformerPredicate
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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 theisEmpty
method on the input object to determine the predicate result.- Parameters:
methodName
- the method name to call on the input object, may not be nullparamTypes
- the parameter typesargs
- the arguments- Returns:
- the predicate
- Throws:
IllegalArgumentException
- if the method name is nullIllegalArgumentException
- if the paramTypes and args don't match- See Also:
InvokerTransformer
,TransformerPredicate
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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 nullpredicate2
- the second predicate, may not be null- Returns:
- the
and
predicate - Throws:
IllegalArgumentException
- if either predicate is null- See Also:
AndPredicate
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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 nullIllegalArgumentException
- if any predicate in the array is null- See Also:
AllPredicate
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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 nullIllegalArgumentException
- if any predicate in the collection is null- See Also:
AllPredicate
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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 nullpredicate2
- the second predicate, may not be null- Returns:
- the
or
predicate - Throws:
IllegalArgumentException
- if either predicate is null- See Also:
OrPredicate
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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 nullIllegalArgumentException
- if any predicate in the array is null- See Also:
AnyPredicate
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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 nullIllegalArgumentException
- if any predicate in the collection is null- See Also:
AnyPredicate
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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 nullpredicate2
- the second predicate, may not be null- Returns:
- the
either
predicate - Throws:
IllegalArgumentException
- if either predicate is null- See Also:
OnePredicate
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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 nullIllegalArgumentException
- if any predicate in the array is null- See Also:
OnePredicate
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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 nullIllegalArgumentException
- if any predicate in the collection is null- See Also:
OnePredicate
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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 nullpredicate2
- the second predicate, may not be null- Returns:
- the
neither
predicate - Throws:
IllegalArgumentException
- if either predicate is null- See Also:
NonePredicate
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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 nullIllegalArgumentException
- if any predicate in the array is null- See Also:
NonePredicate
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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 nullIllegalArgumentException
- if any predicate in the collection is null- See Also:
NonePredicate
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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:
NotPredicate
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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:
TransformerPredicate
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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:
NullIsExceptionPredicate
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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:
NullIsFalsePredicate
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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:
NullIsTruePredicate
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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 firstpredicate
- 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:
TransformedPredicate
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