死锁：同步中嵌套同步，但锁不同，例一：

class DeadLockDemo
{
    public static void main(String[] args)
    {
        Thread t1 = new Thread(new Test(true));
        Thread t2 = new Thread(new Test(false));
        
        t1.start();
        t2.start();
    }
}

class Test implements Runnable
{
    private boolean flag;
    public Test(boolean flag)
    {
        this.flag = flag;
    }
    
    public void run()
    {
        if(flag)
        {
            synchronized(Locks.object1)
                {
                    System.out.println("if object1");
                    synchronized(Locks.object2)
                    {
                        System.out.println("if object2");
                    }
                }
        }    
        else
        {
            synchronized(Locks.object2)
                {
                    System.out.println("else object2");
                    synchronized(Locks.object1)
                    {
                        System.out.println("else object1");
                    }
                }
        }
    }
}

class Locks
{
    static Object object1 = new Object();
    static Object object2 = new Object();
}