我想在对象上使用一种只打印尚未收到的数字的方法，因此我使用了以下代码。这个想法是我使用一个映射，它为每个整数存储一个锁，如果它已经在映射中，则线程等待锁，否则它将以该整数作为键和Integer对象作为新的锁到映射中价值，
注意：我Integer(a)用作整数的锁a
问题是我想释放地图的锁，我想等待从地图中检索到的锁，但是race condition发生了，有什么想法可以解决这个问题吗？
public class sync_print {
public static void main(String[] args) {
sync_print syobj = new sync_print();
Thread t1 = new Thread(new worker(syobj, 10) , "thread 1");
Thread t2 = new Thread(new worker(syobj, 10) , "thread 2");
Thread t3 = new Thread(new worker(syobj, 4) , "thread 3");
Thread t4 = new Thread(new worker(syobj, 5) , "thread 4");
Thread t5 = new Thread(new worker(syobj, 5) , "thread 5");
t1.start();
t2.start();
t3.start();
t4.start();
t5.start();
}
HashMap<Integer, Integer> lock_map = new HashMap<Integer , Integer>();
void print(int a) throws InterruptedException{
synchronized(lock_map){
Integer lock = lock_map.get(a);
if (lock != null){
synchronized (lock) {
System.out.println(Thread.currentThread().getName() + " is waiting");
lock_map.notify();
lock.wait();
}
}else{
lock_map.put(a, new Integer(a));
System.out.println(a);
}
}
}
}
class worker implements Runnable{
int val;
sync_print obj;
public worker(sync_print obj , int v){
this.val = v;
this.obj = obj;
}
public void run() {
try {
obj.print(val);
} catch (InterruptedException e) {}
}
}