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Java classes for temporal testing and concurrency

There is a newer version: 1.1

/*
 * Copyright (c) 2009-2010, tempus-fugit committers
 *
 * Licensed 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 com.google.code.tempusfugit.concurrency;

import java.io.PrintStream;
import java.lang.management.ManagementFactory;
import java.lang.management.ThreadInfo;
import java.lang.management.ThreadMXBean;
import java.util.List;

import static java.lang.String.format;
import static java.util.Arrays.asList;
import static java.util.Collections.emptyList;

/**
 * Detect Java-level deadlocks.
 * 
 * Java 1.5 only supports finding monitor based deadlocks. 1.6's {@link ThreadMXBean} supports {@link java.util.concurrent.locks.Lock}
 * based deadlocks.
 */
public class DeadlockDetector {

    private static final ThreadMXBean mbean = ManagementFactory.getThreadMXBean();

    public static void printDeadlocks(PrintStream writer) {
        List deadlocks = findDeadlocks();
        if (deadlocks.isEmpty())
            return;
        print(writer, deadlocks);
    }

    private static void print(PrintStream writer, List deadlocks) {
        writer.println("Deadlock detected\n=================\n");
        for (ThreadInfo thread : deadlocks) {
            writer.println(format("\"%s\":", thread.getThreadName()));
            writer.println(format("  waiting to lock Monitor of %s ", thread.getLockName()));
            writer.println(format("  which is held by \"%s\"", thread.getLockOwnerName()));
            writer.println();
        }
    }

    private static List findDeadlocks() {
        long[] monitorDeadlockedThreads = mbean.findMonitorDeadlockedThreads();
        if (monitorDeadlockedThreads == null)
            return emptyList();
        return asList(mbean.getThreadInfo(monitorDeadlockedThreads));
    }

}