core/src/main/java/org/apache/commons/functor/core/algorithm/GeneratorContains.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.functor.core.algorithm;

import java.io.Serializable;

import org.apache.commons.functor.BinaryPredicate;
import org.apache.commons.functor.Predicate;
import org.apache.commons.functor.Procedure;
import org.apache.commons.functor.generator.Generator;

/**
 * Tests whether a {@link Generator} contains an element that matches a {@link Predicate}.
 *
 * @param <T> the predicate argument type.
 * @version $Revision$ $Date$
 */
public final class GeneratorContains<T> implements BinaryPredicate<Generator<? extends T>, Predicate<? super T>>,
        Serializable {
    /**
     * serialVersionUID declaration.
     */
    private static final long serialVersionUID = -1539983619621733276L;
    /**
     * A static {@link GeneratorContains} instance reference.
     */
    private static final GeneratorContains<Object> INSTANCE = new GeneratorContains<Object>();

    /**
     * Helper procedure.
     *
     * @param <T> the predicate argument type.
     */
    private static class ContainsProcedure<T> implements Procedure<T> {
        /**
         * The wrapped predicate.
         */
        private final Predicate<? super T> pred;
        /**
         * Flag to mark if the wrapped predicate succeeded or not.
         */
        private boolean found;

        /**
         * Create a new ContainsProcedure.
         *
         * @param pred The wrapped predicate
         */
        public ContainsProcedure(Predicate<? super T> pred) {
            this.pred = pred;
        }

        /**
         * {@inheritDoc}
         */
        public void run(T obj) {
            found |= pred.test(obj);
        }
    }

    /**
     * {@inheritDoc}
     * @param left Generator
     * @param right Predicate
     */
    public boolean test(Generator<? extends T> left, Predicate<? super T> right) {
        ContainsProcedure<T> findProcedure = new ContainsProcedure<T>(right);
        left.run(findProcedure);
        return findProcedure.found;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public boolean equals(Object obj) {
        return obj == this || obj != null && obj.getClass().equals(getClass());
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public int hashCode() {
        return System.identityHashCode(INSTANCE);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public String toString() {
        return "GeneratorContains";
    }

    /**
     * Get a static {@link GeneratorContains} instance.
     * @return {@link GeneratorContains}
     */
    public static GeneratorContains<Object> instance() {
        return INSTANCE;
    }
}