ChainedClosure.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.Collection;
import java.util.Objects;

import org.apache.commons.collections4.Closure;

/**
 * Closure implementation that chains the specified closures together.
 *
 * @param <T> the type of the input to the operation.
 * @since 3.0
 */
public class ChainedClosure<T> implements Closure<T>, Serializable {

    /** Serial version UID */
    private static final long serialVersionUID = -3520677225766901240L;

    /**
     * Factory method that performs validation and copies the parameter array.
     *
     * @param <E> the type that the closure acts on
     * @param closures  the closures to chain, copied, no nulls
     * @return the {@code chained} closure
     * @throws NullPointerException if the closures array is null
     * @throws NullPointerException if any closure in the array is null
     */
    public static <E> Closure<E> chainedClosure(final Closure<? super E>... closures) {
        FunctorUtils.validate(closures);
        if (closures.length == 0) {
            return NOPClosure.<E>nopClosure();
        }
        return new ChainedClosure<>(closures);
    }

    /**
     * Create a new Closure that calls each closure in turn, passing the
     * result into the next closure. The ordering is that of the iterator()
     * method on the collection.
     *
     * @param <E> the type that the closure acts on
     * @param closures  a collection of closures to chain
     * @return the {@code chained} closure
     * @throws NullPointerException if the closures collection is null
     * @throws NullPointerException if any closure in the collection is null
     */
    @SuppressWarnings("unchecked")
    public static <E> Closure<E> chainedClosure(final Collection<? extends Closure<? super E>> closures) {
        Objects.requireNonNull(closures, "closures");
        if (closures.isEmpty()) {
            return NOPClosure.<E>nopClosure();
        }
        // convert to array like this to guarantee iterator() ordering
        final Closure<? super E>[] cmds = new Closure[closures.size()];
        int i = 0;
        for (final Closure<? super E> closure : closures) {
            cmds[i++] = closure;
        }
        FunctorUtils.validate(cmds);
        return new ChainedClosure<>(false, cmds);
    }

    /** The closures to call in turn */
    private final Closure<? super T>[] iClosures;

    /**
     * Hidden constructor for the use by the static factory methods.
     *
     * @param clone  if {@code true} the input argument will be cloned
     * @param closures  the closures to chain, no nulls
     */
    private ChainedClosure(final boolean clone, final Closure<? super T>... closures) {
        iClosures = clone ? FunctorUtils.copy(closures) : closures;
    }

    /**
     * Constructor that performs no validation.
     * Use {@code chainedClosure} if you want that.
     *
     * @param closures  the closures to chain, copied, no nulls
     */
    public ChainedClosure(final Closure<? super T>... closures) {
        this(true, closures);
    }

    /**
     * Execute a list of closures.
     *
     * @param input  the input object passed to each closure
     */
    @Override
    public void execute(final T input) {
        for (final Closure<? super T> iClosure : iClosures) {
            iClosure.accept(input);
        }
    }

    /**
     * Gets the closures.
     *
     * @return a copy of the closures
     * @since 3.1
     */
    public Closure<? super T>[] getClosures() {
        return FunctorUtils.copy(iClosures);
    }

}