多线程协作打印 （完美世界2017秋招真题）

建立m个线程，每个线程只能打印一种字符，要求线程同时运行，交替打印n次字符。

比如: n=3 m=2打印字符为A和B。要求线程1打印3次A，线程2打印3次B，在屏幕输出ABABAB

注意: 需要检查输入有效性，遇到错误输入时，请打印error并安全退出。

import java.util.Scanner;

public class Main {
	public static int count = 0;

	public static void main(String args[]) {
		Scanner sc = new Scanner(System.in);
		int n;
		String s;
		while (sc.hasNextInt()) {
			n = sc.nextInt();
			s = sc.next();
			if (!(n + "").matches("\\+?[1-9][0-9]*") || s == null
					|| s.length() <= 0) {
				System.out.println("error");
				return;
			} else {
				Object ob = new Object();
				for (int i = 0; i < s.length(); i++) {
					new MyThread(s.charAt(i), i, s.length(), ob).start();
				}
			}
		}
	}

	static class MyThread extends Thread {
		char c;
		int index;
		int length;
		Object ob;

		public MyThread(char c, int index, int length, Object ob) {
			this.c = c;
			this.index = index;
			this.length = length;
			this.ob = ob;
		}

		@Override
		public void run() {
			print();
		}

		public void print() {
			synchronized (ob) {
				for (int i = 0; i < length; i++) {
					while (count % length != index) {
						try {
							ob.wait();
						} catch (InterruptedException e) {
							e.printStackTrace();
						}
					}
					System.out.print(c);
					count++;
					ob.notifyAll();
				}
			}

		}
	}
}