测试类：
package com.koow.kkwwo.test;
public class MyRunnable extends Thread {
public static void main(String[] args) {
Thread ta = new MyRunnable();
Thread tb = new MyRunnable();
ta.start();
tb.start();
}
public void run() {
Foo f = new Foo();
f.getX();
}
}
package com.koow.kkwwo.test;
public class Foo {
public int getX() {
synchronized (this) {
System.out.println("开始");
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("结束");
}
return 0;
}
}
执行以上代码会发现线程锁并没有起作用
原因MyRunnable中run方法new新的对象
修改MyRunnable类，修改为
package com.koow.kkwwo.test;
public class MyRunnable extends Thread {
Foo f=null;
public MyRunnable(Foo f){
this.f=f;
}
public static void main(String[] args) {
Foo f = new Foo();
Thread ta = new MyRunnable(f);
Thread tb = new MyRunnable(f);
ta.start();
tb.start();
}
public void run() {
f.getX();
}
}
再次运行，会发现线程锁起作用，由此得出synchronized (this)锁住的是对象
如果想锁住方法，如下
package com.koow.kkwwo.test;
public class Foo {
public static synchronized int getX() {
System.out.println("开始");
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("结束");
return 0;
}
}
package com.koow.kkwwo.test;
public class MyRunnable extends Thread {
public static void main(String[] args) {
Thread ta = new MyRunnable();
Thread tb = new MyRunnable();
ta.start();
tb.start();
}
public void run() {
Foo f = new Foo();
f.getX();
}
}
或者
package com.koow.kkwwo.test;
public class Foo {
public int getX() {
synchronized (Foo.class) {
System.out.println("开始");
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("结束");
}
return 0;
}
}
这两种都可以实现