GridClosure3.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.ignite.internal.util.lang;

import org.apache.ignite.internal.util.typedef.C3;

/**
 * Defines generic {@code for-each} type of closure. Closure is a first-class function that is defined with
 * (or closed over) its free variables that are bound to the closure scope at execution. Since
 * Java 6 doesn't provide a language construct for first-class function the closures are implemented
 * as abstract classes.
 * <h2 class="header">Type Alias</h2>
 * To provide for more terse code you can use a typedef {@link C3} class or various factory methods in
 * {@link GridFunc} class. Note, however, that since typedefs in Java rely on inheritance you should
 * not use these type aliases in signatures.
 * <h2 class="header">Thread Safety</h2>
 * Note that this interface does not impose or assume any specific thread-safety by its
 * implementations. Each implementation can elect what type of thread-safety it provides,
 * if any.
 * @param <E1> Type of the first free variable, i.e. the element the closure is called or closed on.
 * @param <E2> Type of the second free variable, i.e. the element the closure is called or closed on.
 * @param <E3> Type of the third free variable, i.e. the element the closure is called or closed on.
 * @param <R> Type of the closure's return value.
 * @see C3
 * @see GridFunc
 */
public interface GridClosure3<E1, E2, E3, R> {
    /**
     * Closure body.
     *
     * @param e1 First bound free variable, i.e. the element the closure is called or closed on.
     * @param e2 Second bound free variable, i.e. the element the closure is called or closed on.
     * @param e3 Third bound free variable, i.e. the element the closure is called or closed on.
     * @return Optional return value.
     */
    public R apply(E1 e1, E2 e2, E3 e3);
}