代碼詳解の多線程下的代碼死鎖

一、main函數

package com.sdmjhca.springBootDemo.deadlock;

import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/**
 * @author JHMI on 2017/8/20 0020.
 * 此種生成死鎖的方式注意下列問題：
 * 1、測試類內部定義的對象不能是靜態的
 * 2、synchronized必須是嵌套鎖
 */
public class DeadLockMain {
    public static void main(String args[]) throws InterruptedException {
        /*DeadLoakTest t1 = new DeadLoakTest(true);

        DeadLoakTest t2 = new DeadLoakTest(false);
        t1.start();
        t2.start();*/
        /*ExecutorService executor = Executors.newCachedThreadPool();
        executor.execute(t1);
        executor.execute(t2);*/
        Object o1 = new String("11111111111111111");
        Object o2 = new String("22222222222222");
        DeadLoakTest2 test2 = new DeadLoakTest2(o1,o2);
        //Thread.sleep(1000);
        DeadLoakTest2 test21 = new DeadLoakTest2(o2,o1);
        test2.start();
        test21.start();

    }
}

二、兩種測試類寫法

package com.sdmjhca.springBootDemo.deadlock;

/**
 * @author JHMI on 2017/8/20 0020.
 */
public class DeadLoakTest extends Thread {
    boolean flag;
    public DeadLoakTest(boolean temp){
        flag = temp;
    }
    public void run(){
        if(flag){
            lock(Resource.o1,Resource.o2);
        }else{
            lock(Resource.o2,Resource.o1);
        }
    }
    public void lock(Object o1,Object o2){
        synchronized (o1){
            System.out.println("已經獲得對象1的鎖，"+o1);
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            synchronized (o2){
                System.out.println("已經獲得對象2的鎖,"+o2);
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }

            }
        }
    }
}

package com.sdmjhca.springBootDemo.deadlock;

/**
 * @author JHMI on 2017/8/20 0020.
 * 此種生成死鎖的方式注意下列問題：
 * 1、測試類內部定義的對象不能是靜態的
 * 2、synchronized必須是嵌套鎖
 */
public class DeadLoakTest2 extends Thread {
    boolean flag;
    //局部變量是線程私有的
     Object o1;
     Object o2;
    /**
     * 此處注意不能使用static修飾符，
     */
    //static靜態變量和常量是線程公有的
    static Object o3;
    static Object o4;


    public DeadLoakTest2(boolean temp){
        flag = temp;
    }
    public DeadLoakTest2(Object o1,Object o2){
        this.o1 = o1;
        this.o2 = o2;
    }
    public void run(){
        lock(o1,o2);
    }
    public void lock(Object o1,Object o2){
        synchronized (o1){
            System.out.println("已經獲得對象1的鎖，"+o1);
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            synchronized (o2){
                System.out.println("已經獲得對象2的鎖,"+o2);
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }

            }
        }

    }
}

package com.sdmjhca.springBootDemo.deadlock;


/**
 * @author JHMI on 2017/8/20 0020.
 */
public class Resource {
    static final Object o1 = new String("1111");
    static final Object o2 = new String("2222");
}