死锁

• 线程死锁原理图：

• 锁对象 LockA

package com.yonyou.sci.gateway.exec.sisuo;

public class LockA {

    // 构造方法私有化，控制这个锁对象不能使用 new 来创建
    private LockA(){};

    static final LockA locka = new LockA();

}

• 锁对象 LockB

package com.yonyou.sci.gateway.exec.sisuo;

public class LockB {

    // 构造方法私有化，控制这个锁对象不能使用 new 来创建
    private LockB(){};

    static final LockB lockb = new LockB();

}

• Runnable接口实现死锁代码

package com.yonyou.sci.gateway.exec.sisuo;

/**
 * 实现死锁代码
 * 运行 if 里面的 LockA.locka是，这时候执行 else 的 LockB.lockb 方法，就会出现死锁的情况
 */
public class LockRunnable implements Runnable {
    int i = 0;

    @Override
    public void run () {
        while (true) {
            if( i%2 == 0){
                synchronized (LockA.locka){
                    System.out.println("if...locka");
                    synchronized (LockB.lockb) {
                        System.out.println("if...lockb");
                    }
                }
            }
            else {
                synchronized (LockB.lockb){
                    System.out.println("else...lockb");
                    synchronized (LockA.locka){
                        System.out.println("else...locka");
                    }
                }
            }
            i++;
        }
    }
    
}

• 运行死锁代码

package com.yonyou.sci.gateway.exec.sisuo;

public class LockMain {

    public static void main (String[] args) {
        LockRunnable lr = new LockRunnable();

        Thread t1 = new Thread(lr);
        Thread t2 = new Thread(lr);

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

}