题目描述：
控制三个线程，按顺序在“Hello”字符串后添加“_A”，“_B”,"_C" ,输出 “Hello_A_B_C”;
实现方法：使用wait()和notifyAll()方法实现；
核心思想：在A线程运行完成时，同时设置B线程执行的条件，并唤醒(使用notifyAll())其他所有阻塞的线程，当A线程执行完后，如果获得CPU时间片的线程是B线程，则执行，如果不是，则使用wait()方法让该线程挂起。这样就可以保证线程执行的顺序。
运行结果：
代码：
代码语言：javascript复制/**
*
*/
package com.cherish.createThread;
import java.util.Scanner;
import java.util.concurrent.Callable;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
/**
* @author CherishTheYouth
*
*/
public class TongCheng{
public static void main(String[] args)
{
TongCheng tc = new TongCheng();
HelloABC hello = tc.new HelloABC("hello");
ExecutorService es = Executors.newFixedThreadPool(3);
es.execute(tc.new PrintThread(hello,"A") );
es.execute(tc.new PrintThread(hello,"B") );
es.execute(tc.new PrintThread(hello,"C") );
es.shutdown();
}
public class HelloABC{
private String str = null;
private String nextStr = "A"; //用于控制线程调用的顺序
public HelloABC(String str)
{
this.str = str;
}
public void print()
{
System.out.println(str);
}
public String getString()
{
return str;
}
public void setString(String s)
{
str = new StringBuffer(str).append("_").append(s).toString();
}
public void setNextString(String current)
{
switch(current) {
case "A":
nextStr = "B";
break;
case "B":
nextStr = "C";
break;
case "C" :
nextStr = "A";
break;
}
}
}
public class PrintThread implements Runnable{
private HelloABC hello = null;
private String letter;
public PrintThread(HelloABC hello,String letter)
{
this.hello = hello;
this.letter = letter;
}
@Override
public void run() {
// TODO 自动生成的方法存根
for(int i = 0;i< 3;i )
{
synchronized (hello) {
if(hello.nextStr.equals(letter))
{
hello.setString(letter);
hello.setNextString(letter);
hello.print();
hello.notifyAll();
}else
{
try {
hello.wait();
} catch (InterruptedException e) {
// TODO: handle exception
e.printStackTrace();
}
}
}
}
}
}
}
