Java如何使用线程解决死锁？

在Java编程中，如何使用线程解决死锁？

以下示例演示如何使用线程的概念解决死锁问题。

// from W w w .Y I I b  AI.c  o  M
package com.yiibai;

import java.util.*;
import java.util.concurrent.*;
import java.util.concurrent.locks.*;

public class SolvingDeadlock extends ReentrantLock {
    private static List deadlockLocksRegistry = new ArrayList();

    private static synchronized void registerLock(SolvingDeadlock ddl) {
        if (!deadlockLocksRegistry.contains(ddl))
            deadlockLocksRegistry.add(ddl);
    }

    private static synchronized void unregisterLock(SolvingDeadlock ddl) {
        if (deadlockLocksRegistry.contains(ddl))
            deadlockLocksRegistry.remove(ddl);
    }

    private List hardwaitingThreads = new ArrayList();

    private static synchronized void markAsHardwait(List l, Thread t) {
        if (!l.contains(t))
            l.add(t);
    }

    private static synchronized void freeIfHardwait(List l, Thread t) {
        if (l.contains(t))
            l.remove(t);
    }

    private static Iterator getAllLocksOwned(Thread t) {
        SolvingDeadlock current;
        ArrayList results = new ArrayList();
        Iterator itr = deadlockLocksRegistry.iterator();

        while (itr.hasNext()) {
            current = (SolvingDeadlock) itr.next();
            if (current.getOwner() == t)
                results.add(current);
        }
        return results.iterator();
    }

    private static Iterator getAllThreadsHardwaiting(SolvingDeadlock l) {
        return l.hardwaitingThreads.iterator();
    }

    private static synchronized boolean canThreadWaitOnLock(Thread t, SolvingDeadlock l) {

        Iterator locksOwned = getAllLocksOwned(t);
        while (locksOwned.hasNext()) {
            SolvingDeadlock current = (SolvingDeadlock) locksOwned.next();
            if (current == l)
                return false;
            Iterator waitingThreads = getAllThreadsHardwaiting(current);

            while (waitingThreads.hasNext