从java中的另一个类访问静态变量

Question

I had a queue implemented as linked list in my multithreaded server. I want to access this queue from another class. Both classes are in the same package. I tried making this queue as public static and accessing it through getter, but without success Can somebody tell me what is the exact problem.

This is my code: Queue Declaration:

public static Queue<Request> q=new ConcurrentLinkedQueue<Request>();

public static void setQ(Queue<Request> q) {
        Connection.q = q;
    }

    public static Queue<Request> getQ() {
        return q;
    }

Accesing Queue:

Queue<Request> queue=new ConcurrentLinkedQueue<Request>(); 
queue=Connection.getQ();

Adding Value to Queue in thread of connection

q.add(r);

Answer 1

You can access a public static member of another class directly, using the notation ClassName.memberName :

public class Foo {
    public static String bar = "hi there";
}

public class Thing {
    public static void main(String[] args) {
        System.out.println(Foo.bar); // "hi there"
   }
}

public static data members are usually not a great idea (unless they've final ), but if you need one, that's how you do it.

Answer 2

You should be able to access if directly, or using static getter methods...

If this is your Queue class...

public class Queue {
    public static LinkedList myList = new LinkedList();

    public static ListedList getMyList(){
        return myList;
    }
}

Then you could access your list be either calling Queue.myList or Queue.getMyList() - both will do the same thing. The benefit of using a getter method would be that you can control access to the list, such as by making the method synchronized , preventing calls to the list being out of order.