死鎖

什么是死鎖

兩個或兩個以上的線程在執(zhí)行過程中，因?yàn)闋帄Z資源而造成一種相互等待的現(xiàn)象

死鎖的原因

系統(tǒng)資源不足
線程運(yùn)行推進(jìn)的順序不合理
資源分配不當(dāng)

手寫死鎖

package com.hz.xhf;

public class HoldLockThread implements Runnable {

    private String lockA;
    private String lockB;

    public HoldLockThread(String lockA, String lockB) {
        this.lockA = lockA;
        this.lockB = lockB;
    }

    @Override
    public void run() {
        synchronized (lockA){
            System.out.println(Thread.currentThread().getName() + "拿到" + lockA + "鎖，嘗試獲取" + lockB + "鎖");
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            synchronized (lockB){
                System.out.println(Thread.currentThread().getName() + "拿到" + lockB + "鎖，嘗試獲取" + lockA + "鎖");
            }
        }
    }
}

package com.hz.xhf;

public class DeadLockTest {
    public static void main(String[] args) {
        String lockA = "lockA";
        String lockB = "lockB";

        new Thread(new HoldLockThread(lockA, lockB), "ThreadA").start();
        new Thread(new HoldLockThread(lockB, lockA), "ThreadB").start();
    }
}

解決死鎖方法

jps -l 定位進(jìn)程號
jstack XXX 查錯