題目描述

Java代碼模擬死鎖

死鎖條件

• 互斥使用：一個(gè)資源只能分配給一個(gè)線程
• 不可剝奪：資源只能由占有者釋放，申請(qǐng)者不能強(qiáng)制剝奪
• 請(qǐng)求保持：線程申請(qǐng)資源時(shí)，保持對(duì)原有資源的占有
• 循環(huán)等待：存在一個(gè)進(jìn)程等待隊(duì)列：{P1 , P2 , … , Pn}, 其中P1等待P2占有的資源，P2等待P3占有的資源，…，Pn等待P1占有的資源，形成一個(gè)進(jìn)程等待環(huán)路
  代碼

思路

• 定義兩個(gè)資源o1，o2
• 對(duì)象deadLock1占有資源o1，需要資源o2
• 對(duì)象deadLock2占有資源o2，需要資源o1
• 死鎖產(chǎn)生

代碼

public class DeadLock implements Runnable {

    // flag=1，占有對(duì)象o1，等待對(duì)象o2
    // flag=0，占有對(duì)象o2，等待對(duì)象o1
    public int flag = 1;

    // 定義兩個(gè)Object對(duì)象，模擬兩個(gè)線程占有的資源
    public static Object o1 = new Object();
    public static Object o2 = new Object();

    public static void main(String[] args) {

        DeadLock deadLock1 = new DeadLock();
        DeadLock deadLock2 = new DeadLock();

        deadLock1.flag = 0;
        deadLock2.flag = 1;

        Thread thread1 = new Thread(deadLock1);
        Thread thread2 = new Thread(deadLock2);

        thread1.start();
        thread2.start();

    }

    public void run() {

        System.out.println("flag: " + flag);

        // deadLock2占用資源o1，準(zhǔn)備獲取資源o2
        if (flag == 1) {
            synchronized (o1) {
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                synchronized (o2) {
                    System.out.println("1");
                }
            }
        }

        // deadLock1占用資源o2，準(zhǔn)備獲取資源o1
        else if (flag == 0) {
            synchronized (o2) {
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                synchronized (o1) {
                    System.out.println("0");
                }
            }
        }
    }
}