两个线程轮流打印数字，一直到100

创建一个类，定义两个静态全局变量：

static int num=1;
static Integer in=new Integer(1);

让这个类继承Thread类
重写Thread类里面的run()方法
因为使用两个线程，为了防止数据重复，使用同步synchronized。

@Override
public void run() {
        while (true){
            synchronized (in){
                if (num>100){
                    System.exit(0);
                }else {
                    System.out.println(num);
                    num++;
                }
            }
        }
}

创建main()方法
声明两个线程，分别调用start()方法

public static void main(String[] args) {
    Demo1 d1=new Demo1();
    d1.start();
    Demo1 d2=new Demo1();
    d2.start();
}

执行结果：

方法1：

package cn.hp.thread.homewoke;
//1. 两个线程轮流打印数字，一直到100
public class Work1 implements Runnable{
    static int num=0;
    static Boolean flag=true;
    static Object o=new Object();

    @Override
    public void run() {

    synchronized (o){
        while (num<100){
        num++;
        if (true){
            flag=false;
            System.out.println("t1:"+num);
        }else {
            flag=true;
            System.out.println("t2:"+num);
        }
    }}
    }



    public static void main(String[] args) {

        Thread t1 = new Thread(new Work1());
        t1.start();
        Thread t2 = new Thread(new Work1());
        t2.start();

    }
}

方法2：

public class Work1{
    static int num=101;
static Work1 w=new Work1();
    public static void main(String[] args) {
    //定义两个线程
        Thread t1 = new Thread(new Thread1());
        Thread t2 = new Thread(new Thread2());
        t1.start();
        t2.start();
    }

    public static class Thread1 implements Runnable{

        @Override
        public void run() {

            while (true){
                synchronized (w) {//synchronized()  括弧内部是 同步锁对象
                if (num>1){
                    try {
                        w.notify();//一次只能有一个线程拥有对象的监视器(就是绑定了一个监视器来判断是第几个线程)
                        num--;
                        System.out.println("t1:"+num);
                        w.wait();//重新获得对监视器的所有权后继续执行
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }

                }else{
                    System.exit(1);//当num=1退出系统
                }
                }
            }
        }
    }
    public static class Thread2 implements Runnable{

        @Override
        public void run() {
            while (true){
                synchronized (w) {
                    if (num>1){
                        try {
                            w.notify();
                            num--;
                            System.out.println("t2:"+num);
                            w.wait();
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }

                    }else{
                        System.exit(1);
                    }
                }
            }
        }
    }
}

运行结果：

t1:100
t2:99
t1:98
t2:97
t1:96
t2:95
t1:94
t2:93
t1:92
t2:91
t1:90
t2:89
t1:88
t2:87
t1:86
t2:85
t1:84
t2:83
t1:82
t2:81
t1:80
t2:79
t1:78
t2:77
t1:76
t2:75
t1:74
t2:73
t1:72
t2:71
t1:70
t2:69
t1:68
t2:67
t1:66
t2:65
t1:64
t2:63
t1:62
t2:61
t1:60
t2:59
t1:58
t2:57
t1:56
t2:55
t1:54
t2:53
t1:52
t2:51
t1:50
t2:49
t1:48
t2:47
t1:46
t2:45
t1:44
t2:43
t1:42
t2:41
t1:40
t2:39
t1:38
t2:37
t1:36
t2:35
t1:34
t2:33
t1:32
t2:31
t1:30
t2:29
t1:28
t2:27
t1:26
t2:25
t1:24
t2:23
t1:22
t2:21
t1:20
t2:19
t1:18
t2:17
t1:16
t2:15
t1:14
t2:13
t1:12
t2:11
t1:10
t2:9
t1:8
t2:7
t1:6
t2:5
t1:4
t2:3
t1:2
t2:1

Process finished with exit code 1

罗马字母对照表作为参考
10,40,50,90,100都是特殊处理的分界线

#include"stdafx.h"
#include<stdio.h>


int main()
{   
	int num[7] = { 1, 5,10,50,100,500,1000 }; //罗马数字转换模板
	char str[7] = { 'I','V','X','L','C','D','M' };
	char rom[10][5] = { "\0", "I","II","III","IV","V","VI","VII","VIII\0","IX"};
	for (int j = 1;j <= 100;j++)
	{
		int i = j;
		while (i)
		{   
			if (i < 10)
			{
				puts(rom[i]);
				i = 0;
			}
			if (i == 100) {
				puts("C");
				i = 0;
			}
			if (i >= 90)
			{
				putchar('X');
				putchar('C');
				i -= 90;
			}
			if (i >= 50)
			{
				putchar(str[3]);
				i -= 50;
			}
			if (i >= 40)
			{
				putchar('L');
				putchar('X');
				i -= 40;
			}
			while (i >= 10)
			{
				putchar('X');
				i -= 10;
			}
		}
		printf("\n");
	}
	return 0;
}