Java線程-線程八鎖

synchronized在方法上加鎖

1. 加在非靜態方法上。鎖住的是this對象

class Test{
	public synchronized void test(){}
	}

等價於

class Test{
	public void test(){
		synchronized(this){
		}
	}
}
		

2. 加在靜態方法上。鎖住的是類對象。

class Test{
	public synchronized static void test(){
	}
}

等價於

class Test{
	public static void test(){
		synchronized(Test.class){
		}	
	}
}

線程八鎖

爲了體現出這個 1s的輸出，可以在Number類方法a裏面，debug輸出一些值。

1.

輸出順序：12 或21或者同時輸出

public class Demo{
    private static Logger logger = Logger.getLogger(Demo.class);
    public static void  main(String[] agrs) throws InterruptedException {
        Number n1=new Number();
        new Thread(()->{n1.a();},"t1").start();
        new Thread(()->{n1.b();},"t2").start();
    }

}
class Number{
    private static Logger logger = Logger.getLogger(Number.class);
    public synchronized  void a(){
        logger.debug("1");
    }
    public synchronized  void b(){
        logger.debug("2");
    }
}

2.

輸出順序的可能情況：

• 等待1秒，輸出12
• 輸出2，等1秒，輸出1

public class Demo{
    private static Logger logger = Logger.getLogger(Demo.class);
    public static void  main(String[] agrs) throws InterruptedException {
        Number n1=new Number();
         new Thread(()->{
            try {
                n1.a();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        },"t1").start();
        new Thread(()->{n1.b();},"t2").start();
    }
	
}
class Number{
    private static Logger logger = Logger.getLogger(Number.class);
    public synchronized  void a() throws InterruptedException {
        Thread.sleep(1000);
        logger.debug("1");
    }
    public synchronized  void b(){
        logger.debug("2");
    }
}

3.

3 等一秒，12
3 2 等一秒，1
2 3 等一秒，1

import org.apache.log4j.Logger;
public class Demo{
    private static Logger logger = Logger.getLogger(Demo.class);
    public static void  main(String[] agrs) throws InterruptedException {
        Number n1=new Number();
        new Thread(()->{
            try {
                n1.a();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        },"t1").start();
        new Thread(()->{n1.b();},"t2").start();
        new Thread(()->{n1.c();},"t3").start();
    }

}
class Number{
    private static Logger logger = Logger.getLogger(Number.class);
    public synchronized  void a() throws InterruptedException {
        Thread.sleep(1000);
        logger.debug("1");
    }
    public synchronized  void b(){
        logger.debug("2");
    }
    public void c(){
        logger.debug("3");
    }
}

4.

2 等一秒 1
解釋：鎖住的不同的對象。
t1和t2並行。由於t1睡眠的時候，t2還在運行，所以先輸出2

public class Demo{
    private static Logger logger = Logger.getLogger(Demo.class);
    public static void  main(String[] agrs) throws InterruptedException {
        Number n1=new Number();
        Number n2=new Number();
        new Thread(()->{
            try {
                n1.a();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        },"t1").start();
        new Thread(()->{n2.b();},"t2").start();
    }

}
class Number{
    private static Logger logger = Logger.getLogger(Number.class);
    public synchronized  void a() throws InterruptedException {
        Thread.sleep(1000);
        logger.debug("1");
    }
    public synchronized  void b(){
        logger.debug("2");
    }
}

5.

鎖住不同的對象。
2 等一秒 1

public class Demo{
    private static Logger logger = Logger.getLogger(Demo.class);
    public static void  main(String[] agrs) throws InterruptedException {
        Number n1=new Number();
        Number n2=new Number();
        new Thread(()->{
            try {
                n1.a();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        },"t1").start();//鎖住Number類對象
        new Thread(()->{n2.b();},"t2").start();//鎖住n1對象
    }

}
class Number{
    private static Logger logger = Logger.getLogger(Number.class);
    public synchronized  static void a() throws InterruptedException {
        Thread.sleep(1000);
        logger.debug("1");
    }
    public synchronized  void b(){
        logger.debug("2");
    }
}

6.

鎖住的同一個對象，存在互斥。
1s 12 或者 2 1s 1

public class Demo{
    private static Logger logger = Logger.getLogger(Demo.class);
    public static void  main(String[] agrs) throws InterruptedException {
        Number n1=new Number();
        new Thread(()->{
            try {
                n1.a();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        },"t1").start();
        new Thread(()->{n1.b();},"t2").start();
    }
}
class Number{
    private static Logger logger = Logger.getLogger(Number.class);
    public synchronized  static void a() throws InterruptedException {
        Thread.sleep(1000);
        logger.debug("1");
    }
    public synchronized static void b(){
        logger.debug("2");
    }
}

7.

不存在互斥，2 1s 1

import org.apache.log4j.Logger;
public class Demo{
    private static Logger logger = Logger.getLogger(Demo.class);
    public static void  main(String[] agrs) throws InterruptedException {
        Number n1=new Number();
        Number n2=new Number();
        new Thread(()->{
            try {
                n1.a();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        },"t1").start();
        new Thread(()->{n2.b();},"t2").start();
    }

}
class Number{
    private static Logger logger = Logger.getLogger(Number.class);
    public synchronized  static void a() throws InterruptedException {
        Thread.sleep(1000);
        logger.debug("1");
    }
    public synchronized  void b(){
        logger.debug("2");
    }
}

8.

鎖住的同一個對象，存在互斥。
1s 12 或者 2 1s 1

public class Demo{
    private static Logger logger = Logger.getLogger(Demo.class);
    public static void  main(String[] agrs) throws InterruptedException {
        Number n1=new Number();
        Number n2=new Number();
        new Thread(()->{
            try {
                n1.a();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        },"t1").start();
        new Thread(()->{n2.b();},"t2").start();
    }

}
class Number{
    private static Logger logger = Logger.getLogger(Number.class);
    public synchronized  static void a() throws InterruptedException {
        Thread.sleep(1000);
        logger.debug("1");
    }
    public synchronized static void b(){
        logger.debug("2");
    }
}