Java面试题(2) 两个线程，交替打印100次A和B
目录
-
- 一、实现方式一
-
- 实现思路：
- 代码实现：
- 执行结果：
- 二、实现方式二
-
- 实现思路：
- 代码实现：
- 执行结果：
- 三、思考
一、实现方式一
实现思路：
代码实现：
ThreadTest.java
package com.demo.example;
public class ThreadTest {
public static void main(String[] args) {
MyThread threadA = new MyThread();
MyThread threadB = new MyThread();
threadA.setThread(threadB);
threadA.setKey("A");
threadB.setThread(threadA);
threadB.setKey("B");
threadA.start();
threadB.start();
}
}
class MyThread extends Thread {
private final Object lock = new Object();
private MyThread thread;
private String key;
public void setThread(MyThread thread) {
this.thread = thread;
}
public void setKey(String key) {
this.key = key;
}
public void getLock() {
synchronized (lock) {
try {
lock.wait();
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
}
}
public void releaseLock() {
synchronized (lock) {
lock.notify();
}
}
@Override
public void run() {
for (int i = 0; i < 50; i++) {
System.out.println(Thread.currentThread().getName() + ", " + key + ",count: " + (i + 1));
thread.releaseLock();
if (i < 49) {
this.getLock();
}
}
}
}
执行结果：
Thread-0, A,count: 1
Thread-1, B,count: 1
Thread-0, A,count: 2
Thread-1, B,count: 2
Thread-0, A,count: 3
Thread-1, B,count: 3
Thread-0, A,count: 4
Thread-1, B,count: 4
Thread-0, A,count: 5
Thread-1, B,count: 5
Thread-0, A,count: 6
Thread-1, B,count: 6
Thread-0, A,count: 7
Thread-1, B,count: 7
Thread-0, A,count: 8
Thread-1, B,count: 8
Thread-0, A,count: 9
Thread-1, B,count: 9
Thread-0, A,count: 10
Thread-1, B,count: 10
Thread-0, A,count: 11
Thread-1, B,count: 11
Thread-0, A,count: 12
Thread-1, B,count: 12
Thread-0, A,count: 13
Thread-1, B,count: 13
Thread-0, A,count: 14
Thread-1, B,count: 14
Thread-0, A,count: 15
Thread-1, B,count: 15
Thread-0, A,count: 16
Thread-1, B,count: 16
Thread-0, A,count: 17
Thread-1, B,count: 17
Thread-0, A,count: 18
Thread-1, B,count: 18
Thread-0, A,count: 19
Thread-1, B,count: 19
Thread-0, A,count: 20
Thread-1, B,count: 20
Thread-0, A,count: 21
Thread-1, B,count: 21
Thread-0, A,count: 22
Thread-1, B,count: 22
Thread-0, A,count: 23
Thread-1, B,count: 23
Thread-0, A,count: 24
Thread-1, B,count: 24
Thread-0, A,count: 25
Thread-1, B,count: 25
Thread-0, A,count: 26
Thread-1, B,count: 26
Thread-0, A,count: 27
Thread-1, B,count: 27
Thread-0, A,count: 28
Thread-1, B,count: 28
Thread-0, A,count: 29
Thread-1, B,count: 29
Thread-0, A,count: 30
Thread-1, B,count: 30
Thread-0, A,count: 31
Thread-1, B,count: 31
Thread-0, A,count: 32
Thread-1, B,count: 32
Thread-0, A,count: 33
Thread-1, B,count: 33
Thread-0, A,count: 34
Thread-1, B,count: 34
Thread-0, A,count: 35
Thread-1, B,count: 35
Thread-0, A,count: 36
Thread-1, B,count: 36
Thread-0, A,count: 37
Thread-1, B,count: 37
Thread-0, A,count: 38
Thread-1, B,count: 38
Thread-0, A,count: 39
Thread-1, B,count: 39
Thread-0, A,count: 40
Thread-1, B,count: 40
Thread-0, A,count: 41
Thread-1, B,count: 41
Thread-0, A,count: 42
Thread-1, B,count: 42
Thread-0, A,count: 43
Thread-1, B,count: 43
Thread-0, A,count: 44
Thread-1, B,count: 44
Thread-0, A,count: 45
Thread-1, B,count: 45
Thread-0, A,count: 46
Thread-1, B,count: 46
Thread-0, A,count: 47
Thread-1, B,count: 47
Thread-0, A,count: 48
Thread-1, B,count: 48
Thread-0, A,count: 49
Thread-1, B,count: 49
Thread-0, A,count: 50
Thread-1, B,count: 50
二、实现方式二
实现思路：
代码实现：
ThreadTest.java
package com.demo.example;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class ThreadTest {
public static void main(String[] args) {
// 写法一：显示创建Thread
Runnable runnable = new AbThread();
Thread threadA = new Thread(runnable);
Thread threadB = new Thread(runnable);
threadA.start();
threadB.start();
// 写法二：使用线程池
// ExecutorService executorService = Executors.newCachedThreadPool();
// executorService.execute(runnable);
// executorService.execute(runnable);
}
}
class AbThread implements Runnable {
char[] content = {'A', 'B'};
int count = 0;
@Override
public void run() {
synchronized (this) {
try {
while(count < 100) {
System.out.println(Thread.currentThread().getName() + ", " + content[count % 2] + ",count: " + (++count));
notify();
if (count < 100) {
wait();
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
执行结果：
Thread-0, A,count: 1
Thread-1, B,count: 2
Thread-0, A,count: 3
Thread-1, B,count: 4
Thread-0, A,count: 5
Thread-1, B,count: 6
Thread-0, A,count: 7
Thread-1, B,count: 8
Thread-0, A,count: 9
Thread-1, B,count: 10
Thread-0, A,count: 11
Thread-1, B,count: 12
Thread-0, A,count: 13
Thread-1, B,count: 14
Thread-0, A,count: 15
Thread-1, B,count: 16
Thread-0, A,count: 17
Thread-1, B,count: 18
Thread-0, A,count: 19
Thread-1, B,count: 20
Thread-0, A,count: 21
Thread-1, B,count: 22
Thread-0, A,count: 23
Thread-1, B,count: 24
Thread-0, A,count: 25
Thread-1, B,count: 26
Thread-0, A,count: 27
Thread-1, B,count: 28
Thread-0, A,count: 29
Thread-1, B,count: 30
Thread-0, A,count: 31
Thread-1, B,count: 32
Thread-0, A,count: 33
Thread-1, B,count: 34
Thread-0, A,count: 35
Thread-1, B,count: 36
Thread-0, A,count: 37
Thread-1, B,count: 38
Thread-0, A,count: 39
Thread-1, B,count: 40
Thread-0, A,count: 41
Thread-1, B,count: 42
Thread-0, A,count: 43
Thread-1, B,count: 44
Thread-0, A,count: 45
Thread-1, B,count: 46
Thread-0, A,count: 47
Thread-1, B,count: 48
Thread-0, A,count: 49
Thread-1, B,count: 50
Thread-0, A,count: 51
Thread-1, B,count: 52
Thread-0, A,count: 53
Thread-1, B,count: 54
Thread-0, A,count: 55
Thread-1, B,count: 56
Thread-0, A,count: 57
Thread-1, B,count: 58
Thread-0, A,count: 59
Thread-1, B,count: 60
Thread-0, A,count: 61
Thread-1, B,count: 62
Thread-0, A,count: 63
Thread-1, B,count: 64
Thread-0, A,count: 65
Thread-1, B,count: 66
Thread-0, A,count: 67
Thread-1, B,count: 68
Thread-0, A,count: 69
Thread-1, B,count: 70
Thread-0, A,count: 71
Thread-1, B,count: 72
Thread-0, A,count: 73
Thread-1, B,count: 74
Thread-0, A,count: 75
Thread-1, B,count: 76
Thread-0, A,count: 77
Thread-1, B,count: 78
Thread-0, A,count: 79
Thread-1, B,count: 80
Thread-0, A,count: 81
Thread-1, B,count: 82
Thread-0, A,count: 83
Thread-1, B,count: 84
Thread-0, A,count: 85
Thread-1, B,count: 86
Thread-0, A,count: 87
Thread-1, B,count: 88
Thread-0, A,count: 89
Thread-1, B,count: 90
Thread-0, A,count: 91
Thread-1, B,count: 92
Thread-0, A,count: 93
Thread-1, B,count: 94
Thread-0, A,count: 95
Thread-1, B,count: 96
Thread-0, A,count: 97
Thread-1, B,count: 98
Thread-0, A,count: 99
Thread-1, B,count: 100
三、思考
如果是三个线程，交替打印100次ABC，怎么实现？
参考地址：
1.两个线程交替打印100次AB，https://blog.csdn.net/qq_34707456/article/details/103027820
2.两个线程交替打印1-100的奇数和偶数，https://blog.csdn.net/bobo1356/article/details/103408137
3.线程交替输出0-100，https://blog.csdn.net/zhangxiao123qqq/article/details/112842059