這邊是一個簡單的執行緒呼叫

public class SynchronizedThis {

    public static void main(String[] args) {

        ThisLock thisLock = new ThisLock();
        new Thread("T1") {
            @Override
            public void run() {
                thisLock.m1();
            }
        }.start();

        new Thread("T2") {
            @Override
            public void run() {
                thisLock.m2();
            }
        }.start();
    }
}

class ThisLock {
    
    public void m1() {
            try {
                System.out.println(Thread.currentThread().getName());
                Thread.sleep(10_000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
    }

    public void m2() {
            try {
                System.out.println(Thread.currentThread().getName());
                Thread.sleep(10_000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
    }
}
 

從輸出可以看出T1,T2是同時輸出的，下面加上sychronized改造一下

​
class ThisLock {

    private final Object LOCK = new Object();

    public  void m1() {
        synchronized(this) {
            System.out.println(this.getClass().getName());
            try {
                System.out.println(Thread.currentThread().getName());
                Thread.sleep(10_000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

    }

    public synchronized void m2() {
            try {
                System.out.println(Thread.currentThread().getName());
                Thread.sleep(10_000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
    }
}

​
 

發現這兩個鎖的是同一個東西,所以一個先輸出一個後輸出

class ThisLock {

    private final Object LOCK = new Object();

    public  void m1() {
        synchronized(LOCK) {
            try {
                System.out.println(Thread.currentThread().getName());
                Thread.sleep(10_000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

    }

    public  synchronized void m2() {
            try {
                System.out.println(Thread.currentThread().getName());
                Thread.sleep(10_000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
    }
}
​
 

最後鎖的是一個物件，然後輸出發現是同時輸出的，說明是兩個不同的鎖，一個是LOCK鎖，一個是this鎖