题目

编写一个Java程序,该程序将启动4个线程,其中3个是掷硬币线程,1个是主线程。每个掷硬币线程将连续掷出若干次硬币(10次以内,次数随机生成);主线程将打印出正面出现的总次数以及正面出现的概率。

难点

因为要计算数量以及出现概率，所以必须将所有子线程内的数据同步到主线程内。

源代码

Coin.java

package com.web.homework03; public class Coin{ public static void main(String[] args) throws InterruptedException {         test test = com.web.homework03.test.getTest();         Thread[] trr = new Thread[3]; for (int i = 0; i < 3; i++) {             trr[i] = new Thread(new Roll(test), "线程" + (i + 1)); } for (Thread thread : trr) {             thread.start(); } for (Thread thread : trr) {             thread.join(); }         System.out.println("正面总次数为："+test.getRoll());         System.out.println("正面总次数为："+test.getRandoms());         System.out.println("出现正面的概率为："+(double)test.getRoll()/test.getRandoms()); } } 

Roll.java

package com.web.homework03; public class Roll implements Runnable{ private test test01; public Roll(test test){ this.test01 = test; } @Override public void run() {         test01.method(); } } 

test.java

package com.web.homework03; import java.util.Random; public class test { private int randoms; private int roll; public int getRandoms() { return randoms; } public void setRandoms(int randoms) { this.randoms = randoms; } public int getRoll() { return roll; } public void setRoll(int roll) { this.roll = roll; } private test() { } private static final test test = new test(); public static test getTest() { return test; } public synchronized void method() {         Random random = new Random(); int times = random.nextInt(10);         randoms += times; for (int i =0;i<times;i++){ if (random.nextBoolean()){                 roll++; } } } }