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feilong is a suite of core and expanded libraries that include utility classes, http, excel,cvs, io classes, and much much more.
/*
* 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 com.feilong.lib.collection4.functors;
import java.io.Serializable;
import java.util.Comparator;
import org.apache.commons.collections4.Predicate;
/**
* Predicate that compares the input object with the one stored in the predicate using a comparator.
* In addition, the comparator result can be evaluated in accordance to a supplied criterion value.
*
*
* In order to demonstrate the use of the predicate, the following variables are declared:
*
*
*
*
* Integer ONE = Integer.valueOf(1);
*
* Integer TWO = Integer.valueOf(2);
*
* Comparator comparator = new Comparator(){
*
* public int compare(Object first,Object second){
* return ((Integer) second) - ((Integer) first);
* }
*
* };
*
*
*
* Using the declared variables, the ComparatorPredicate can be used used in the
* following way:
*
*
*
* ComparatorPredicate.comparatorPredicate(ONE, comparator).evaluate(TWO);
*
*
*
* The input variable TWO in compared to the stored variable ONE using
* the supplied comparator. This is the default usage of the predicate and will return
* true if the underlying comparator returns 0. In addition to the default
* usage of the predicate, it is possible to evaluate the comparator's result in several ways. The
* following {@link Criterion} enumeration values are provided by the predicate:
*
*
*
* - EQUAL
* - GREATER
* - GREATER_OR_EQUAL
* - LESS
* - LESS_OR_EQUAL
*
*
*
* The following examples demonstrates how these constants can be used in order to manipulate the
* evaluation of a comparator result.
*
*
*
* ComparatorPredicate.comparatorPredicate(ONE, comparator,ComparatorPredicate.Criterion.GREATER).evaluate(TWO);
*
*
*
* The input variable TWO is compared to the stored variable ONE using the supplied comparator
* using the GREATER evaluation criterion constant. This instructs the predicate to
* return true if the comparator returns a value greater than 0.
*
*
* @param
*
* @since 4.0
*/
public class ComparatorPredicate implements Predicate,Serializable{
private static final long serialVersionUID = -1863209236504077399L;
public enum Criterion{
EQUAL, GREATER, LESS, GREATER_OR_EQUAL, LESS_OR_EQUAL,
}
// Instance variables:
/** The internal object to compare with */
private final T object;
/** The comparator to use for comparison */
private final Comparator comparator;
/** The comparison evaluation criterion to use */
private final Criterion criterion;
/**
* Factory to create the comparator predicate
*
* @param
* the type that the predicate queries
* @param object
* the object to compare to
* @param comparator
* the comparator to use for comparison
* @return the predicate
* @throws NullPointerException
* if comparator is null
*/
public static Predicate comparatorPredicate(final T object,final Comparator comparator){
return comparatorPredicate(object, comparator, Criterion.EQUAL);
}
/**
* Factory to create the comparator predicate
*
* @param
* the type that the predicate queries
* @param object
* the object to compare to
* @param comparator
* the comparator to use for comparison
* @param criterion
* the criterion to use to evaluate comparison
* @return the predicate
* @throws NullPointerException
* if comparator or criterion is null
*/
public static Predicate comparatorPredicate(final T object,final Comparator comparator,final Criterion criterion){
if (comparator == null){
throw new NullPointerException("Comparator must not be null.");
}
if (criterion == null){
throw new NullPointerException("Criterion must not be null.");
}
return new ComparatorPredicate<>(object, comparator, criterion);
}
/**
* Constructor that performs no validation.
* Use comparatorPredicate if you want that.
*
* @param object
* the object to compare to
* @param comparator
* the comparator to use for comparison
* @param criterion
* the criterion to use to evaluate comparison
*/
public ComparatorPredicate(final T object, final Comparator comparator, final Criterion criterion){
super();
this.object = object;
this.comparator = comparator;
this.criterion = criterion;
}
/**
* Evaluates the predicate. The predicate evaluates to true in the following cases:
*
*
* comparator.compare(object, input) == 0 && criterion == EQUALcomparator.compare(object, input) < 0 && criterion == LESScomparator.compare(object, input) > 0 && criterion == GREATERcomparator.compare(object, input) >= 0 && criterion == GREATER_OR_EQUALcomparator.compare(object, input) <= 0 && criterion == LESS_OR_EQUAL
*
* @see org.apache.commons.collections4.Predicate#evaluate(java.lang.Object)
* @see java.util.Comparator#compare(java.lang.Object first, java.lang.Object second)
*
* @param target
* the target object to compare to
* @return {@code true} if the comparison succeeds according to the selected criterion
* @throws IllegalStateException
* if the criterion is invalid (really not possible)
*/
@Override
public boolean evaluate(final T target){
boolean result = false;
final int comparison = comparator.compare(object, target);
switch (criterion) {
case EQUAL:
result = comparison == 0;
break;
case GREATER:
result = comparison > 0;
break;
case LESS:
result = comparison < 0;
break;
case GREATER_OR_EQUAL:
result = comparison >= 0;
break;
case LESS_OR_EQUAL:
result = comparison <= 0;
break;
default:
throw new IllegalStateException("The current criterion '" + criterion + "' is invalid.");
}
return result;
}
}