有人能解释一下,为什么这里的synchronized块
没有锁定变量_c
?
public class static_thread implements Runnable{
private static Integer _c=0;
public static void main(String[] args) throws Throwable {
for(int i=0;i<100000;i++){
if(i%2==0){_c++;}
}
System.out.println("one thread: "+_c);
Thread[] t=new Thread[50];
_c=0;
for(int i=0;i<t.length;i++){
t[i]=new Thread(new static_thread(i, i*(100000/50)));
t[i].start();
}
for(Thread _:t){_.join();}
System.out.println("+one thread: "+_c);//wrong answer!
}
public void run() {
for(int i=s;i<(s+l);i++){
if(i%2==0){
synchronized (_c) {//y u no lock?!
_c++;//Inconsistence, not thread-safe, so what is synchronized block is doing here?
}
}
}
}
int s,l;
public static_thread(int s, int l) {
this.s = s;
this.l = l;
}
}
每次运行,我都会得到新的错误值。