Java Thread Runnable run

Question

请问 为什么主函数中的User eclipse 会提示修改成 final 修饰
class User {
public void A(){
for (int i = 0; i >0 ; i--) {
System.out.println(i);
}
}
public void B(){
for (int i = 0; i >0 ; i--) {
System.out.println(i);
}
}
}

public class TestThread {
public static void main(String[] args) {
final User u = new User();
Thread t1 = new Thread(new Runnable(){public void run(){u.A();}});
Thread t2 = new Thread(new Runnable(){public void run(){u.B();}});

}

}

Answer 1

异步中修改外部对象，会导致不同步，造成数据错误，所以建议你改成final，保证对象是不会被修改的