解析Java線程同步鎖的選擇方法

2019-11-26 16:06:50

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來源：轉載

供稿：網友

在需要線程同步的時候如何選擇合適的線程鎖？
例：選擇可以存入到常量池當中的對象，String對象等　　

public class SyncTest
{
    private String name = "name";
public void method(String flag)
    {
        synchronized (name)
        {
            System.out.println(flag + ", invoke method ....");
            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();

    }

}

線程類：

復制代碼代碼如下:

public class MyThread1 extends Thread
{
    SyncTest syncTest;

    @Override
    public void run()
    {
        syncTest.method(this.getName());
    }
}

本來應該是要實現線程thread1和thread2同步，線程thread3和thread4同步的，但結果呢？
卻是使得線程thread1、thread2、thread3、thread4同步了，很是郁悶。
我推薦選用的同步鎖對象：

復制代碼代碼如下:

package com.rcx.thread;

public class SyncTest
{
    // 特殊的instance變量,用于充當同步鎖的對象
    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();

    }