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Java example source code file (PromiseCombiner.java)

This example Java source code file (PromiseCombiner.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

adding, already, genericfuturelistener, illegalstateexception, override, promise, promisecombiner, suppresswarnings, throwable

The PromiseCombiner.java Java example source code

/*
 * Copyright 2016 The Netty Project
 *
 * The Netty Project 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 io.netty.util.concurrent;

import io.netty.util.internal.ObjectUtil;

public final class PromiseCombiner {
    private int expectedCount;
    private int doneCount;
    private boolean doneAdding;
    private Promise<Void> aggregatePromise;
    private Throwable cause;
    private final GenericFutureListener<Future listener = new GenericFutureListener>() {
        @Override
        public void operationComplete(Future<?> future) throws Exception {
            ++doneCount;
            if (!future.isSuccess() && cause == null) {
                cause = future.cause();
            }
            if (doneCount == expectedCount && doneAdding) {
                tryPromise();
            }
        }
    };

    @SuppressWarnings({ "unchecked", "rawtypes" })
    public void add(Promise promise) {
        checkAddAllowed();
        ++expectedCount;
        promise.addListener(listener);
    }

    @SuppressWarnings({ "unchecked", "rawtypes" })
    public void addAll(Promise... promises) {
        checkAddAllowed();
        expectedCount += promises.length;
        for (Promise promise : promises) {
            promise.addListener(listener);
        }
    }

    public void finish(Promise<Void> aggregatePromise) {
        if (doneAdding) {
            throw new IllegalStateException("Already finished");
        }
        doneAdding = true;
        this.aggregatePromise = ObjectUtil.checkNotNull(aggregatePromise, "aggregatePromise");
        if (doneCount == expectedCount) {
            tryPromise();
        }
    }

    private boolean tryPromise() {
        return (cause == null) ? aggregatePromise.trySuccess(null) : aggregatePromise.tryFailure(cause);
    }

    private void checkAddAllowed() {
        if (doneAdding) {
            throw new IllegalStateException("Adding promises is not allowed after finished adding");
        }
    }
}

Other Java examples (source code examples)

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