请教JAVA高手！关于线程的同步机制synchronized 用法
public   class   threadDemo   extends   Thread   {  
int   flag;  
public   threadDemo(String   name,int   f){  
super(name);  
this.flag=f;  
}  
public   void   run(){  
char   ch;  
System.out.println();  
System.out.print(getName()+ "   start:   ");  
synchronized(this){  
if(flag==0){  

for(ch= 'a ';ch <= 'z ';ch++)  
System.out.print(ch+ "   ");  
}  

else  
if(flag==1){  
for(ch= 'A ';ch <= 'Z ';ch++)  
System.out.print(ch+ "   ");  
}  
System.out.print(getName()+ "   end! ");  
}  
}  

public   static   void   main   (String[]   args)   {  
threadDemo   t1=   new   threadDemo( "线程1 ",1);  
threadDemo   t2=   new   threadDemo( "线程2 ",0);  
t1.start();  
t2.start();  
System.out.println( "active:   "+t1.activeCount());  
}  
}  

我想让这个程序按同步机制对象t1,t2分别输出字母的大小写。当t1的进程执行完后，在执行t2的进程。但是不行，不知道哪里出了问题，请高手指教


------解决方案--------------------
你这个程序锁的对象不同，一个是对t1加锁，另一个是对t2加锁，所以就不会有同步，我把你的程序改了改，你可以试试：

public class threadDemo extends Thread {
int flag;

public static Object lock = new Object();

public threadDemo(String name, int f) {
super(name);
this.flag = f;
}

public void run() {
char ch;
synchronized (lock) {
System.out.print(getName() + " start: ");
if (flag == 0) {

for (ch = 'a '; ch <= 'z '; ch++)
System.out.print(ch + " ");
}

else if (flag == 1) {
for (ch = 'A '; ch <= 'Z '; ch++)
System.out.print(ch + " ");
}
System.out.println(getName() + " end! ");
}
}

public static void main(String[] args) {
threadDemo t1 = new threadDemo( "线程1 ", 1);
threadDemo t2 = new threadDemo( "线程2 ", 0);
t1.start();
t2.start();
System.out.println( "active: " + t1.activeCount());
}
}