java并发编程核心方法与框架 怎么样

楼主出现问题有2点：
1. wake() 这个方法也要同步啊，加关键字synchronized ；
2. 第一次调用st（）方法后，available应该保持不变，这样才能保证线程b也打印..start，所以加个if判断一下就ok啦。

public class abc {

 boolean available=false;
 string name;
 int count=0;
 public abc(string name){
 this.name=name;
 }
 public synchronized void st(){
 system.out.println("... start.");
 count++;
 if(count>1){
 available=true;
 }
 try{
 wait();
 }catch(exception e){}
 system.out.println("... end.");
 }
 public synchronized void end(){
 system.out.println("... end.");
 }
 public synchronized void wake() {
 notifyall();
 }

 public static void main(string[] args) {
 // todo auto-generated method stub
 abc x=new abc("haha");
 testthread a=new testthread(x);
 testthread b=new testthread(x);
 c c=new c(x);
 (new thread(a)).start();
 (new thread(b)).start();
 (new thread(c)).start();
 }
 }
 class testthread implements runnable{
 abc abc;
 public testthread(abc abc){
 this.abc=abc;
 }
 public void run(){
 if(!abc.available){
 abc.st();
 }
 else abc.end();

 }
 }
 class c implements runnable{
 abc abc;
 public c(abc abc){
 this.abc=abc;
 }
 public void run(){
 try{
 thread.sleep(1000);
 // system.out.println("sjlfsj jfsdl j"); //验证是否执行到这里
 }catch(interruptedexception e){};
 abc.wake();
 }
 }