迅雷笔试题 （JAVA多线程）启动三个线程，分别打印A B C，现在写一个程序 循环打印ABCABCABC

题目：http://wenku.baidu.com/view/d66187aad1f34693daef3e8a.html

启动三个线程，分别打印A B C，现在写一个程序 循环打印ABCABCABC....

本文分别使用wait、nofity和Semaphore来实现：

wait、nofity版本

public class TestThread {

    public static void main(String[] args) {
        new Thread(new OrderThread(0,'A')).start();
        new Thread(new OrderThread(1,'B')).start();
        new Thread(new OrderThread(2,'C')).start();
    }
}

class OrderThread implements Runnable {
    //定义一个类静态变量的锁对象
    private static Object o = new Object();
    //类静态变量、用来记录是哪个线程进入运行
    private static int count = 0;
    //每个线程的标识，名称
    private char ID;
    //用来控制是线程运行的标识
    private int id;
    //每个线程运行的次数
    private int num = 0;

    public OrderThread(int id,char ID) {
        this.id = id;
        this.ID = ID;
    }

    public void run() {
        synchronized (o) {
            while (num < 10) {
                if(count % 3 == id){
                    System.out.print(ID);
                    ++ count;
                    ++ num;
                    o.notifyAll();
                }
                else{
                    try {
                        o.wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
    }
}

Semaphore版本

public class ThreadSync {
    static class ConditionThread extends Thread {
        private Semaphore preCond;
        private Semaphore postCond;

        ConditionThread(Semaphore preCond, Semaphore postCond, String name) {
            this.preCond = preCond;
            this.postCond = postCond;
            this.setName(name);
        }

        public void run() {
            for (int i = 0; i < 10; i++) {
                try {
                    preCond.acquire();
                    System.out.print(Thread.currentThread().getName());
                    postCond.release();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    public static void main(String[] args) throws InterruptedException {
        Semaphore semaphoreA = new Semaphore(0);
        Semaphore semaphoreB = new Semaphore(0);
        Semaphore semaphoreC = new Semaphore(1);

        Thread threadA = new ConditionThread(semaphoreC, semaphoreA, "A");
        Thread threadB = new ConditionThread(semaphoreA, semaphoreB, "B");
        Thread threadC = new ConditionThread(semaphoreB, semaphoreC, "C");

        threadA.start();
        threadB.start();
        threadC.start();

        // threadA.join();
        // threadB.join();
        // threadC.join();
    }
}

2，假如有字符串“6sabcsssfsfs33” ，用最有快速的方法去掉字符“ab3”，不能用java内置字符串方法（indeOf,substring,replaceAll等）

package com.kingdee.al;

public class Test {
    public static void main(String[] args) {

        String str = "6sabcsssfsfs33";
        char[] array = { 'a', 'b', '3' };
        char[] newArray = str.toCharArray();
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < newArray.length; i++) {
            boolean isMatch = false;
            for (char key : array){
                if (newArray[i] == key)
                    isMatch = true;
            }
            if(!isMatch){
                sb.append(newArray[i]);
            }
        }
        System.out.println(sb.toString());

    }
}