大家都知道synchronized是一個(gè)對(duì)象鎖岩榆，所以當(dāng)對(duì)象變化時(shí)各薇，鎖就會(huì)消失，就會(huì)沒有同步效果鳞仙。

請(qǐng)看下面的問題：

package Thread;

/**
 * Created by zhangzheming on 2018/1/15.
 */

public class ChangeLock {

    private String lock = "lock";

    private void method(){
        synchronized (lock){
            try {
                System.out.println("當(dāng)前線程:"+Thread.currentThread().getName()+"開始");
                lock = "lock modify";
                System.out.println("當(dāng)前線程："+Thread.currentThread().getName()+"完成");
            }catch (Exception e){
                e.printStackTrace();
            }
        }
    }

    public static void main(String[] args){
        final ChangeLock locks = new ChangeLock();

        Thread t1 = new Thread(new Runnable() {
            @Override
            public void run() {
                locks.method();
            }
        });

        Thread t2 = new Thread(new Runnable() {
            @Override
            public void run() {
                locks.method();
            }
        });

        t1.start();
        t2.start();
    }
}

結(jié)果是兩個(gè)線程是幾乎是同時(shí)完成任務(wù)寇蚊，為什么呢？
那是因?yàn)樵谶M(jìn)行method方法執(zhí)行時(shí)棍好，鎖對(duì)象改變了仗岸，這樣同步機(jī)制就消失，沒有了同步效果借笙，這樣對(duì)于多線程操作時(shí)扒怖，便是每個(gè)線程對(duì)象都可以同時(shí)進(jìn)行操作。

但是如果我們對(duì)class對(duì)象進(jìn)行修改是否也會(huì)有上述情況呢业稼？
答案是否定的盗痒。

package Thread;

/**
 * Created by zhangzheming on 2018/1/15.
 */

public class ModifyLock {

    private String name;
    private int age;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public synchronized void changeAttribute(String name,int age){
        try{
            System.out.println("當(dāng)前線程："+Thread.currentThread().getName()+"開始");
            this.setName(name);
            this.setAge(age);

            System.out.println("當(dāng)前線程："+Thread.currentThread().getName()+"修改對(duì)象內(nèi)容為："+this.getName()+","+this.getAge());
            Thread.sleep(2000);
            System.out.println("當(dāng)前線程："+Thread.currentThread().getName()+"結(jié)束");
        }catch (Exception e){
            e.printStackTrace();
        }
    }

    public static void main(String[] args){
        final ModifyLock locks = new ModifyLock();

        Thread t1 = new Thread(new Runnable() {
            @Override
            public void run() {
                locks.changeAttribute("zhangsan",34);
            }
        },"t1");

        Thread t2 = new Thread(new Runnable() {
            @Override
            public void run() {
                locks.changeAttribute("lisi",345);
            }
        },"t2");

        t1.start();
        t2.start();
    }
}

結(jié)果

所以對(duì)于類對(duì)象的屬性進(jìn)行修改，并不影響鎖的效果低散！