Java 学习笔记之 Synchronized锁对象-白红宇

Java 学习笔记之 Synchronized锁对象

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发布时间：2019-06-28

本文共 3927 字，大约阅读时间需要 13 分钟。

Synchronized锁对象：

Synchronized取得的锁都是对象锁，而不是把一段代码或方法当作锁，哪个线程执行带synchronized关键字的方法，哪个线程就持有该方法所属对象的锁，那么其他线程只能等待，前提是多个线程访问的是同一个对象。

实验得出以下结论：

A线程先持有object对象的Lock锁，B线程可以以异步的方式调用object对象中的非synchronized类型的方法。

public class Sync1Object {    synchronized public void methodA() {        try {            System.out.println("begin methodA threadName = "                    + Thread.currentThread().getName());            Thread.sleep(5000);            System.out.println("A end endTime = " + System.currentTimeMillis());        } catch (InterruptedException e) {            e.printStackTrace();        }    }     public void methodB() {        try {            System.out.println("begin methodB threadName = "                    + Thread.currentThread().getName() + " begin time = "                    + System.currentTimeMillis());            Thread.sleep(3000);            System.out.println("B end");        } catch (InterruptedException e) {            e.printStackTrace();        }    }}public class Sync1ThreadA extends Thread{    private Sync1Object object;    public Sync1ThreadA(Sync1Object object) {        this.object = object;    }    @Override    public void run() {        super.run();        object.methodA();    }}public class Sync1ThreadB extends Thread{    private Sync1Object object;    public Sync1ThreadB(Sync1Object object) {        this.object = object;    }    @Override    public void run() {        super.run();        object.methodB();    }}public class ThreadRunMain {    public static void main(String[] args) {        testSync1Thread();    }    public static void testSync1Thread(){        try {            Sync1Object object = new Sync1Object();            Sync1ThreadA a = new Sync1ThreadA(object);            a.setName("A");            a.start();            Thread.sleep(100);            Sync1ThreadB b = new Sync1ThreadB(object);            b.setName("B");            b.start();        } catch (InterruptedException e) {            e.printStackTrace();        }    }}

运行结果：

A线程先持有object对象的Lock锁，B线程如果在这个时候调用object对象中的synchronized类型的方法则需要等待，同步串行执行。

public class Sync1Object {    synchronized public void methodA() {        try {            System.out.println("begin methodA threadName = "                    + Thread.currentThread().getName());            Thread.sleep(5000);            System.out.println("A end endTime = " + System.currentTimeMillis());        } catch (InterruptedException e) {            e.printStackTrace();        }    }     synchronized public void methodB() {        try {            System.out.println("begin methodB threadName = "                    + Thread.currentThread().getName() + " begin time = "                    + System.currentTimeMillis());            Thread.sleep(3000);            System.out.println("B end");        } catch (InterruptedException e) {            e.printStackTrace();        }    }}public class Sync1ThreadA extends Thread{    private Sync1Object object;    public Sync1ThreadA(Sync1Object object) {        this.object = object;    }    @Override    public void run() {        super.run();        object.methodA();    }}public class Sync1ThreadB extends Thread{    private Sync1Object object;    public Sync1ThreadB(Sync1Object object) {        this.object = object;    }    @Override    public void run() {        super.run();        object.methodB();    }}public class ThreadRunMain {    public static void main(String[] args) {        testSync1Thread();    }    public static void testSync1Thread(){        try {            Sync1Object object = new Sync1Object();            Sync1ThreadA a = new Sync1ThreadA(object);            a.setName("A");            a.start();            Thread.sleep(100);            Sync1ThreadB b = new Sync1ThreadB(object);            b.setName("B");            b.start();        } catch (InterruptedException e) {            e.printStackTrace();        }    }}

运行结果：

转载于:https://www.cnblogs.com/AK47Sonic/p/7710626.html

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