org.apache.commons.collections.functors.SwitchClosure Maven / Gradle / Ivy
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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.functors;
import java.io.Serializable;
import java.util.Iterator;
import java.util.Map;
import org.apache.commons.collections.Closure;
import org.apache.commons.collections.Predicate;
/**
* Closure implementation calls the closure whose predicate returns true,
* like a switch statement.
*
* @since Commons Collections 3.0
* @version $Revision: 646777 $ $Date: 2008-04-10 14:33:15 +0200 (Thu, 10 Apr 2008) $
*
* @author Stephen Colebourne
*/
public class SwitchClosure implements Closure, Serializable {
/** Serial version UID */
private static final long serialVersionUID = 3518477308466486130L;
/** The tests to consider */
private final Predicate[] iPredicates;
/** The matching closures to call */
private final Closure[] iClosures;
/** The default closure to call if no tests match */
private final Closure iDefault;
/**
* Factory method that performs validation and copies the parameter arrays.
*
* @param predicates array of predicates, cloned, no nulls
* @param closures matching array of closures, cloned, no nulls
* @param defaultClosure the closure to use if no match, null means nop
* @return the chained closure
* @throws IllegalArgumentException if array is null
* @throws IllegalArgumentException if any element in the array is null
*/
public static Closure getInstance(Predicate[] predicates, Closure[] closures, Closure defaultClosure) {
FunctorUtils.validate(predicates);
FunctorUtils.validate(closures);
if (predicates.length != closures.length) {
throw new IllegalArgumentException("The predicate and closure arrays must be the same size");
}
if (predicates.length == 0) {
return (defaultClosure == null ? NOPClosure.INSTANCE : defaultClosure);
}
predicates = FunctorUtils.copy(predicates);
closures = FunctorUtils.copy(closures);
return new SwitchClosure(predicates, closures, defaultClosure);
}
/**
* Create a new Closure that calls one of the closures depending
* on the predicates.
*
* The Map consists of Predicate keys and Closure values. A closure
* is called if its matching predicate returns true. Each predicate is evaluated
* until one returns true. If no predicates evaluate to true, the default
* closure is called. The default closure is set in the map with a
* null key. The ordering is that of the iterator() method on the entryset
* collection of the map.
*
* @param predicatesAndClosures a map of predicates to closures
* @return the switch closure
* @throws IllegalArgumentException if the map is null
* @throws IllegalArgumentException if any closure in the map is null
* @throws ClassCastException if the map elements are of the wrong type
*/
public static Closure getInstance(Map predicatesAndClosures) {
Closure[] closures = null;
Predicate[] preds = null;
if (predicatesAndClosures == null) {
throw new IllegalArgumentException("The predicate and closure map must not be null");
}
if (predicatesAndClosures.size() == 0) {
return NOPClosure.INSTANCE;
}
// convert to array like this to guarantee iterator() ordering
Closure defaultClosure = (Closure) predicatesAndClosures.remove(null);
int size = predicatesAndClosures.size();
if (size == 0) {
return (defaultClosure == null ? NOPClosure.INSTANCE : defaultClosure);
}
closures = new Closure[size];
preds = new Predicate[size];
int i = 0;
for (Iterator it = predicatesAndClosures.entrySet().iterator(); it.hasNext();) {
Map.Entry entry = (Map.Entry) it.next();
preds[i] = (Predicate) entry.getKey();
closures[i] = (Closure) entry.getValue();
i++;
}
return new SwitchClosure(preds, closures, defaultClosure);
}
/**
* Constructor that performs no validation.
* Use getInstance if you want that.
*
* @param predicates array of predicates, not cloned, no nulls
* @param closures matching array of closures, not cloned, no nulls
* @param defaultClosure the closure to use if no match, null means nop
*/
public SwitchClosure(Predicate[] predicates, Closure[] closures, Closure defaultClosure) {
super();
iPredicates = predicates;
iClosures = closures;
iDefault = (defaultClosure == null ? NOPClosure.INSTANCE : defaultClosure);
}
/**
* Executes the closure whose matching predicate returns true
*
* @param input the input object
*/
public void execute(Object input) {
for (int i = 0; i < iPredicates.length; i++) {
if (iPredicates[i].evaluate(input) == true) {
iClosures[i].execute(input);
return;
}
}
iDefault.execute(input);
}
/**
* Gets the predicates, do not modify the array.
*
* @return the predicates
* @since Commons Collections 3.1
*/
public Predicate[] getPredicates() {
return iPredicates;
}
/**
* Gets the closures, do not modify the array.
*
* @return the closures
* @since Commons Collections 3.1
*/
public Closure[] getClosures() {
return iClosures;
}
/**
* Gets the default closure.
*
* @return the default closure
* @since Commons Collections 3.1
*/
public Closure getDefaultClosure() {
return iDefault;
}
}