一开始随机数有点问题，用了第一个的，发现是0,1,2 就加了个1，功能基本实现了，不知道效率怎么样，switch嵌套。

package com.itranswarp.learnjava;

import java.util.Scanner;

/**
 * switch实现石头/剪子/布并判断胜负
 */

public class Main {
	public static void main(String[] args) {
		Scanner scanner = new Scanner(System.in);
		String result = "";
		System.out.println("please choice:");
		System.out.println(" 1: Rock");
		System.out.println(" 2: Scissors");
		System.out.println(" 3: Paper");
		// 用户输入:
		int choice = 0;
		choice = scanner.nextInt();
		// 计算机随机数 1, 2, 3:
		int random =  (int)(Math.random()*3) + 1;
		switch (choice) {		
		// TODO:
		case 1: switch (random) {
				case 1: result = "We draw!"; break;
				case 2: result = "You win!"; break;
				case 3: result = "You lose!"; break;
				default:
					result = "System wrong!"; break; 
				};
				break;
		case 2: switch (random) {
				case 1: result = "You lose!"; break;
				case 2: result = "We draw!"; break;
				case 3: result = "You win!"; break;
				default:
					result = "System wrong!"; break; 
				};
				break;
		case 3: switch (random) {
				case 1: result = "You lose!"; break;
				case 2: result = "You win!"; break;
				case 3: result = "We draw!"; break;
				default:
					result = "System wrong!"; break; 
				};
				break;
		default : result = "Please follow the rule"; break; 
		}
		
		//print result
		System.out.println("You play " + choice);
		System.out.println("I play " + random);
		System.out.println(result);		
		scanner.close();
	}
}