[英]Multiple threads working on the same object
我有一个POJO BusStop,上面有公交车站的名称以及那里有多少名乘客。
public class BusStop{
private String name;
private Integer passengers;
//setters getters constructor
public void removePassengers(Integer i){
synchronized(passengers){
this.passengers = this.passengers - i; // right now I allow them to go below zero for the sake of just testing threads;
}
}
public void increasePassengers(Integer i){
synchronized(passengers){
this.passengers = this.passengers + i;
}
}
}
还有一个对象BusRide,其中包含源BusStop,目标BusStop以及该乘车中当前有多少乘客。
public class BusRide implements Runnable{
private BusStop source;
private BusStop destination
private Integer passengers;
public BusRide(BusStop src, BusStop dest){
this.source = src;
this.destination = dest;
}
//setters getters
@Override
public void run(){
setPassengers(15);
this.source.removePassengers(15);
setPassengers(0);
this.destination.increasePassengers(15);
}
}
主班:
public class Main{
public static void main(String[] args){
BusStop a = new BusStop("Bus-stop 1", 50);
BusStop b = new BusStop("Bus-stop 2", 45);
BusStop c = new BusStop("Bus-stop 3", 62);
Thread t1 = new Thread(new BusRide(a,b));
Thread t2 = new Thread(new BusRide(a,c));
}
}
在我的主类中,我想创建2个BusRide线程,这些线程将随机从源BusStop到目标BusStop乘坐乘客。 但是我希望BusRide线程从我给他们的对象中带走乘客,但是他们却拥有自己的BusStop对象实例。 那么,如何使两个线程在我赋予它们的同一BusStop对象上运行?
public void removePassengers(Integer i){
synchronized(passengers){
this.passengers = this.passengers - i; // right now I allow them to go below zero for the sake of just testing threads;
}
}
public void increasePassengers(Integer i){
synchronized(passengers){
this.passengers = this.passengers + i;
}
}
以上是错误的。 它应该是
public synchronized void removePassengers(Integer i){
this.passengers = this.passengers - i; // right now I allow them to go below zero for the sake of just testing threads;
}
public synchronized void increasePassengers(Integer i){
this.passengers = this.passengers + i;
}
确实,您正在对一个乘客进行同步,但是将乘客分配给同步块内的另一个值,从本质上来说,两个线程可以同时调用方法。 如果将其用作锁,请始终使变量为final
。
请尝试这个。 线程未启动。
/ ** * * /包com.philips.webcms.foundation.catalog.products.utils.test;
/ ** * @author AV262488 * /公共类ThreadTest {
/**
* @param args
*/
public static void main(String[] args)
{
BusStop a = new BusStop("Bus-stop 1", 50);
BusStop b = new BusStop("Bus-stop 2", 45);
BusStop c = new BusStop("Bus-stop 3", 62);
Thread t1 = new Thread(new BusRide(a, b));
Thread t2 = new Thread(new BusRide(a, c));
t1.start();
t2.start();
System.out.println(a.getPassengers());
}
}
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