解析Java线程同步锁的选择方法

public class SyncTest
{
    // 特殊的instance变量,用于充当同步锁的对象
    private byte[] lock = new byte[0];

    public void method(String flag)
    {
        synchronized (lock)
        {
            System.out.println(flag + ", invoke method f....");
            try
            {
                Thread.sleep(1000);
            }
            catch (InterruptedException e)
            {
                e.printStackTrace();
            }
        }
    }

    public static void main(String[] args)
    {
        SyncTest test1 = new SyncTest();

        SyncTest test2 = new SyncTest();

        MyThread1 myThread1 = new MyThread1();
        MyThread1 myThread2 = new MyThread1();
        myThread1.syncTest = test1;
        myThread2.syncTest = test1;

        MyThread1 myThread3 = new MyThread1();
        MyThread1 myThread4 = new MyThread1();
        myThread3.syncTest = test2;
        myThread4.syncTest = test2;

        myThread1.start();
        myThread2.start();
        myThread3.start();
        myThread4.start();

    }