Java线程 - 死锁(deadlock)

public class ThreadDeadlockDetector {
    
    //建立定期任务的调度器
    private final Timer threadCheck = new Timer("ThreadDeadLockDector",true);
    
    private final Collection<Listener> listeners = new CopyOnWriteArraySet<Listener>();
    
    private final ThreadMXBean mbean = ManagementFactory.getThreadMXBean();    
    
    private static final int DEFAULT_DEADLOCK_CHECK_PERIOD = 10000;
    
    public ThreadDeadlockDetector(){
        this(DEFAULT_DEADLOCK_CHECK_PERIOD);
    }
    
    public ThreadDeadlockDetector(int deadlockCheckPeriod){
        //建立一个定期核查的任务
        threadCheck.schedule(new TimerTask(){
            @Override
            public void run() {
                checkForDeadlocks();
            }
            
        }, 10, deadlockCheckPeriod);
    }
    
    //一旦返现有死锁，就发出死锁报警
    private void checkForDeadlocks() {
        long[] ids = findDeadlockedThreads();
        if(ids != null && ids.length > 0) {
            Thread[] threads = new Thread[ids.length];
            for(int i=0; i<threads.length; i++){
                threads[i] = findMatchingThread(mbean.getThreadInfo(ids[i]));
            }
            fireDeadlockDetected(threads);
        }
        
    }
    
    //核查是否存在死锁
    private long[] findDeadlockedThreads(){
        if(mbean.isSynchronizerUsageSupported()){
            return mbean.findDeadlockedThreads();
        }else{
            return mbean.findMonitorDeadlockedThreads();
        }
    }
    
    private Thread findMatchingThread(ThreadInfo inf){
        for(Thread thread:Thread.getAllStackTraces().keySet()){
            if(thread.getId() == inf.getThreadId()){
                return thread;
            }
        }
        
        throw new IllegalStateException("Deadlocked Thread not found");

    }
    
    public boolean addListener(Listener l){
        return listeners.add(l);
    }
    
    public boolean removeListener(Listener l){
        return listeners.remove(l);
    }
    
    private void fireDeadlockDetected(Thread[] threads){
        for(Listener l : listeners){
            l.deallockDetected(threads);
        }
    }
    
    public interface Listener {
        void deallockDetected(Thread[] deadlockedThreads);
    }
}