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* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.collections;
import java.util.Collection;
import org.apache.commons.collections.functors.AllPredicate;
import org.apache.commons.collections.functors.AndPredicate;
import org.apache.commons.collections.functors.AnyPredicate;
import org.apache.commons.collections.functors.EqualPredicate;
import org.apache.commons.collections.functors.ExceptionPredicate;
import org.apache.commons.collections.functors.FalsePredicate;
import org.apache.commons.collections.functors.IdentityPredicate;
import org.apache.commons.collections.functors.InstanceofPredicate;
import org.apache.commons.collections.functors.InvokerTransformer;
import org.apache.commons.collections.functors.NonePredicate;
import org.apache.commons.collections.functors.NotNullPredicate;
import org.apache.commons.collections.functors.NotPredicate;
import org.apache.commons.collections.functors.NullIsExceptionPredicate;
import org.apache.commons.collections.functors.NullIsFalsePredicate;
import org.apache.commons.collections.functors.NullIsTruePredicate;
import org.apache.commons.collections.functors.NullPredicate;
import org.apache.commons.collections.functors.OnePredicate;
import org.apache.commons.collections.functors.OrPredicate;
import org.apache.commons.collections.functors.TransformedPredicate;
import org.apache.commons.collections.functors.TransformerPredicate;
import org.apache.commons.collections.functors.TruePredicate;
import org.apache.commons.collections.functors.UniquePredicate;
/**
* 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
* @author Ola Berg
*/
public class PredicateUtils {
/**
* This class is not normally instantiated.
*/
public PredicateUtils() {
super();
}
// Simple predicates
//-----------------------------------------------------------------------------
/**
* Gets a Predicate that always throws an exception.
* This could be useful during testing as a placeholder.
*
* @see org.apache.commons.collections.functors.ExceptionPredicate
*
* @return the predicate
*/
public static Predicate exceptionPredicate() {
return ExceptionPredicate.INSTANCE;
}
/**
* Gets a Predicate that always returns true.
*
* @see org.apache.commons.collections.functors.TruePredicate
*
* @return the predicate
*/
public static Predicate truePredicate() {
return TruePredicate.INSTANCE;
}
/**
* Gets a Predicate that always returns false.
*
* @see org.apache.commons.collections.functors.FalsePredicate
*
* @return the predicate
*/
public static Predicate falsePredicate() {
return FalsePredicate.INSTANCE;
}
/**
* Gets a Predicate that checks if the input object passed in is null.
*
* @see org.apache.commons.collections.functors.NullPredicate
*
* @return the predicate
*/
public static Predicate nullPredicate() {
return NullPredicate.INSTANCE;
}
/**
* Gets a Predicate that checks if the input object passed in is not null.
*
* @see org.apache.commons.collections.functors.NotNullPredicate
*
* @return the predicate
*/
public static Predicate notNullPredicate() {
return NotNullPredicate.INSTANCE;
}
/**
* Creates a Predicate that checks if the input object is equal to the
* specified object using equals().
*
* @see org.apache.commons.collections.functors.EqualPredicate
*
* @param value the value to compare against
* @return the predicate
*/
public static Predicate equalPredicate(Object value) {
return EqualPredicate.getInstance(value);
}
/**
* Creates a Predicate that checks if the input object is equal to the
* specified object by identity.
*
* @see org.apache.commons.collections.functors.IdentityPredicate
*
* @param value the value to compare against
* @return the predicate
*/
public static Predicate identityPredicate(Object value) {
return IdentityPredicate.getInstance(value);
}
/**
* Creates a Predicate that checks if the object passed in is of
* a particular type, using instanceof. A null input
* object will return false.
*
* @see org.apache.commons.collections.functors.InstanceofPredicate
*
* @param type the type to check for, may not be null
* @return the predicate
* @throws IllegalArgumentException if the class is null
*/
public static Predicate instanceofPredicate(Class type) {
return InstanceofPredicate.getInstance(type);
}
/**
* 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.
*
* @see org.apache.commons.collections.functors.UniquePredicate
*
* @return the predicate
*/
public static Predicate uniquePredicate() {
// must return new instance each time
return UniquePredicate.getInstance();
}
/**
* 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.
*
* @see org.apache.commons.collections.functors.InvokerTransformer
* @see org.apache.commons.collections.functors.TransformerPredicate
*
* @param methodName the method name to call on the input object, may not be null
* @return the predicate
* @throws IllegalArgumentException if the methodName is null.
*/
public static Predicate invokerPredicate(String methodName){
// reuse transformer as it has caching - this is lazy really, should have inner class here
return asPredicate(InvokerTransformer.getInstance(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.
*
* @see org.apache.commons.collections.functors.InvokerTransformer
* @see org.apache.commons.collections.functors.TransformerPredicate
*
* @param methodName the method name to call on the input object, may not be null
* @param paramTypes the parameter types
* @param args the arguments
* @return the predicate
* @throws IllegalArgumentException if the method name is null
* @throws IllegalArgumentException if the paramTypes and args don't match
*/
public static Predicate invokerPredicate(String methodName, Class[] paramTypes, Object[] args){
// reuse transformer as it has caching - this is lazy really, should have inner class here
return asPredicate(InvokerTransformer.getInstance(methodName, paramTypes, args));
}
// Boolean combinations
//-----------------------------------------------------------------------------
/**
* Create a new Predicate that returns true only if both of the specified
* predicates are true.
*
* @see org.apache.commons.collections.functors.AndPredicate
*
* @param predicate1 the first predicate, may not be null
* @param predicate2 the second predicate, may not be null
* @return the and predicate
* @throws IllegalArgumentException if either predicate is null
*/
public static Predicate andPredicate(Predicate predicate1, Predicate predicate2) {
return AndPredicate.getInstance(predicate1, predicate2);
}
/**
* 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.
*
* @see org.apache.commons.collections.functors.AllPredicate
*
* @param predicates an array of predicates to check, may not be null
* @return the all predicate
* @throws IllegalArgumentException if the predicates array is null
* @throws IllegalArgumentException if any predicate in the array is null
*/
public static Predicate allPredicate(Predicate[] predicates) {
return AllPredicate.getInstance(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.
*
* @see org.apache.commons.collections.functors.AllPredicate
*
* @param predicates a collection of predicates to check, may not be null
* @return the all predicate
* @throws IllegalArgumentException if the predicates collection is null
* @throws IllegalArgumentException if any predicate in the collection is null
*/
public static Predicate allPredicate(Collection predicates) {
return AllPredicate.getInstance(predicates);
}
/**
* Create a new Predicate that returns true if either of the specified
* predicates are true.
*
* @see org.apache.commons.collections.functors.OrPredicate
*
* @param predicate1 the first predicate, may not be null
* @param predicate2 the second predicate, may not be null
* @return the or predicate
* @throws IllegalArgumentException if either predicate is null
*/
public static Predicate orPredicate(Predicate predicate1, Predicate predicate2) {
return OrPredicate.getInstance(predicate1, predicate2);
}
/**
* 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.
*
* @see org.apache.commons.collections.functors.AnyPredicate
*
* @param predicates an array of predicates to check, may not be null
* @return the any predicate
* @throws IllegalArgumentException if the predicates array is null
* @throws IllegalArgumentException if any predicate in the array is null
*/
public static Predicate anyPredicate(Predicate[] predicates) {
return AnyPredicate.getInstance(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.
*
* @see org.apache.commons.collections.functors.AnyPredicate
*
* @param predicates a collection of predicates to check, may not be null
* @return the any predicate
* @throws IllegalArgumentException if the predicates collection is null
* @throws IllegalArgumentException if any predicate in the collection is null
*/
public static Predicate anyPredicate(Collection predicates) {
return AnyPredicate.getInstance(predicates);
}
/**
* Create a new Predicate that returns true if one, but not both, of the
* specified predicates are true.
*
* @see org.apache.commons.collections.functors.OnePredicate
*
* @param predicate1 the first predicate, may not be null
* @param predicate2 the second predicate, may not be null
* @return the either predicate
* @throws IllegalArgumentException if either predicate is null
*/
public static Predicate eitherPredicate(Predicate predicate1, Predicate predicate2) {
return onePredicate(new Predicate[] { predicate1, predicate2 });
}
/**
* 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.
*
* @see org.apache.commons.collections.functors.OnePredicate
*
* @param predicates an array of predicates to check, may not be null
* @return the one predicate
* @throws IllegalArgumentException if the predicates array is null
* @throws IllegalArgumentException if any predicate in the array is null
*/
public static Predicate onePredicate(Predicate[] predicates) {
return OnePredicate.getInstance(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.
*
* @see org.apache.commons.collections.functors.OnePredicate
*
* @param predicates a collection of predicates to check, may not be null
* @return the one predicate
* @throws IllegalArgumentException if the predicates collection is null
* @throws IllegalArgumentException if any predicate in the collection is null
*/
public static Predicate onePredicate(Collection predicates) {
return OnePredicate.getInstance(predicates);
}
/**
* Create a new Predicate that returns true if neither of the specified
* predicates are true.
*
* @see org.apache.commons.collections.functors.NonePredicate
*
* @param predicate1 the first predicate, may not be null
* @param predicate2 the second predicate, may not be null
* @return the neither predicate
* @throws IllegalArgumentException if either predicate is null
*/
public static Predicate neitherPredicate(Predicate predicate1, Predicate predicate2) {
return nonePredicate(new Predicate[] { predicate1, predicate2 });
}
/**
* 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.
*
* @see org.apache.commons.collections.functors.NonePredicate
*
* @param predicates an array of predicates to check, may not be null
* @return the none predicate
* @throws IllegalArgumentException if the predicates array is null
* @throws IllegalArgumentException if any predicate in the array is null
*/
public static Predicate nonePredicate(Predicate[] predicates) {
return NonePredicate.getInstance(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.
*
* @see org.apache.commons.collections.functors.NonePredicate
*
* @param predicates a collection of predicates to check, may not be null
* @return the none predicate
* @throws IllegalArgumentException if the predicates collection is null
* @throws IllegalArgumentException if any predicate in the collection is null
*/
public static Predicate nonePredicate(Collection predicates) {
return NonePredicate.getInstance(predicates);
}
/**
* Create a new Predicate that returns true if the specified predicate
* returns false and vice versa.
*
* @see org.apache.commons.collections.functors.NotPredicate
*
* @param predicate the predicate to not
* @return the not predicate
* @throws IllegalArgumentException if the predicate is null
*/
public static Predicate notPredicate(Predicate predicate) {
return NotPredicate.getInstance(predicate);
}
// Adaptors
//-----------------------------------------------------------------------------
/**
* Create a new Predicate that wraps a Transformer. The Transformer must
* return either Boolean.TRUE or Boolean.FALSE otherwise a PredicateException
* will be thrown.
*
* @see org.apache.commons.collections.functors.TransformerPredicate
*
* @param transformer the transformer to wrap, may not be null
* @return the transformer wrapping predicate
* @throws IllegalArgumentException if the transformer is null
*/
public static Predicate asPredicate(Transformer transformer) {
return TransformerPredicate.getInstance(transformer);
}
// Null handlers
//-----------------------------------------------------------------------------
/**
* 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.
*
* @see org.apache.commons.collections.functors.NullIsExceptionPredicate
*
* @param predicate the predicate to wrap, may not be null
* @return the predicate
* @throws IllegalArgumentException if the predicate is null.
*/
public static Predicate nullIsExceptionPredicate(Predicate predicate){
return NullIsExceptionPredicate.getInstance(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.
*
* @see org.apache.commons.collections.functors.NullIsFalsePredicate
*
* @param predicate the predicate to wrap, may not be null
* @return the predicate
* @throws IllegalArgumentException if the predicate is null.
*/
public static Predicate nullIsFalsePredicate(Predicate predicate){
return NullIsFalsePredicate.getInstance(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.
*
* @see org.apache.commons.collections.functors.NullIsTruePredicate
*
* @param predicate the predicate to wrap, may not be null
* @return the predicate
* @throws IllegalArgumentException if the predicate is null.
*/
public static Predicate nullIsTruePredicate(Predicate predicate){
return NullIsTruePredicate.getInstance(predicate);
}
// Transformed
//-----------------------------------------------------------------------
/**
* Creates a predicate that transforms the input object before passing it
* to the predicate.
*
* @see org.apache.commons.collections.functors.TransformedPredicate
*
* @param transformer the transformer to call first
* @param predicate the predicate to call with the result of the transform
* @return the predicate
* @throws IllegalArgumentException if the transformer or the predicate is null
* @since Commons Collections 3.1
*/
public static Predicate transformedPredicate(Transformer transformer, Predicate predicate) {
return TransformedPredicate.getInstance(transformer, predicate);
}
}