SwitchClosure.java
/*
* 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.collections4.functors;
import java.io.Serializable;
import java.util.Map;
import java.util.Objects;
import org.apache.commons.collections4.Closure;
import org.apache.commons.collections4.Predicate;
/**
* Closure implementation calls the closure whose predicate returns true,
* like a switch statement.
*
* @since 3.0
*/
public class SwitchClosure<E> implements Closure<E>, Serializable {
/** Serial version UID */
private static final long serialVersionUID = 3518477308466486130L;
/**
* Create a new Closure that calls one of the closures depending
* on the predicates.
* <p>
* 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 <E> the type that the closure acts on
* @param predicatesAndClosures a map of predicates to closures
* @return the {@code switch} closure
* @throws NullPointerException if the map is null
* @throws NullPointerException if any closure in the map is null
* @throws ClassCastException if the map elements are of the wrong type
*/
@SuppressWarnings("unchecked")
public static <E> Closure<E> switchClosure(final Map<Predicate<E>, Closure<E>> predicatesAndClosures) {
Objects.requireNonNull(predicatesAndClosures, "predicatesAndClosures");
// convert to array like this to guarantee iterator() ordering
final Closure<? super E> defaultClosure = predicatesAndClosures.remove(null);
final int size = predicatesAndClosures.size();
if (size == 0) {
return (Closure<E>) (defaultClosure == null ? NOPClosure.<E>nopClosure() : defaultClosure);
}
final Closure<E>[] closures = new Closure[size];
final Predicate<E>[] preds = new Predicate[size];
int i = 0;
for (final Map.Entry<Predicate<E>, Closure<E>> entry : predicatesAndClosures.entrySet()) {
preds[i] = entry.getKey();
closures[i] = entry.getValue();
i++;
}
return new SwitchClosure<>(false, preds, closures, defaultClosure);
}
/**
* Factory method that performs validation and copies the parameter arrays.
*
* @param <E> the type that the closure acts on
* @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 {@code chained} closure
* @throws NullPointerException if array is null
* @throws NullPointerException if any element in the array is null
* @throws IllegalArgumentException if the array lengths of predicates and closures do not match
*/
@SuppressWarnings("unchecked")
public static <E> Closure<E> switchClosure(final Predicate<? super E>[] predicates,
final Closure<? super E>[] closures,
final Closure<? super E> 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 (Closure<E>) (defaultClosure == null ? NOPClosure.<E>nopClosure(): defaultClosure);
}
return new SwitchClosure<>(predicates, closures, defaultClosure);
}
/** The tests to consider */
private final Predicate<? super E>[] iPredicates;
/** The matching closures to call */
private final Closure<? super E>[] iClosures;
/** The default closure to call if no tests match */
private final Closure<? super E> iDefault;
/**
* Hidden constructor for the use by the static factory methods.
*
* @param clone if {@code true} the input arguments will be cloned
* @param predicates array of predicates, no nulls
* @param closures matching array of closures, no nulls
* @param defaultClosure the closure to use if no match, null means nop
*/
private SwitchClosure(final boolean clone, final Predicate<? super E>[] predicates,
final Closure<? super E>[] closures, final Closure<? super E> defaultClosure) {
iPredicates = clone ? FunctorUtils.copy(predicates) : predicates;
iClosures = clone ? FunctorUtils.copy(closures) : closures;
iDefault = defaultClosure == null ? NOPClosure.<E>nopClosure() : defaultClosure;
}
/**
* Constructor that performs no validation.
* Use {@code switchClosure} if you want that.
*
* @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
*/
public SwitchClosure(final Predicate<? super E>[] predicates, final Closure<? super E>[] closures,
final Closure<? super E> defaultClosure) {
this(true, predicates, closures, defaultClosure);
}
/**
* Executes the closure whose matching predicate returns true
*
* @param input the input object
*/
@Override
public void execute(final E input) {
for (int i = 0; i < iPredicates.length; i++) {
if (iPredicates[i].evaluate(input)) {
iClosures[i].execute(input);
return;
}
}
iDefault.execute(input);
}
/**
* Gets the closures.
*
* @return a copy of the closures
* @since 3.1
*/
public Closure<? super E>[] getClosures() {
return FunctorUtils.<E>copy(iClosures);
}
/**
* Gets the default closure.
*
* @return the default closure
* @since 3.1
*/
public Closure<? super E> getDefaultClosure() {
return iDefault;
}
/**
* Gets the predicates.
*
* @return a copy of the predicates
* @since 3.1
*/
public Predicate<? super E>[] getPredicates() {
return FunctorUtils.<E>copy(iPredicates);
}
}