Java多线程—创建Thread类实现多线程

class aa extends Thread{
public aa(String str){
super(str);
}
public void run(){
for(int i=0;i<10;i++){
System.out.println(i+" "+getName());
try{
sleep((int)(Math.random()*1000));
}catch (InterruptedException e){}
}
System.out.println("DONE!"+getName());
}
}

public class bb {
public static void main(String[] args) {
aa s1=new aa("Beijing");
s1.start();
aa s2=new aa("Shanghai");
s2.start();
}
}