Declaring static generic variables in a generic class

Question

I\'ve read that you cannot declare static variables/methods inside a generic class and I really have no idea how to solve my problem or work around it so I ask for your guidance

Answer 1

Try this approach: Define a protected abstract method that subclasses implement to return a static object for their class.

There may be some logic issues etc, but the basics of the answer are here (ie this compiles):

EDITED: Now delegating to HeadAndTail

/**  A subclass of Nexus */
abstract class Nexus> { // This syntax lets you confine T to a subclass of Nexus
    private T next;

    protected Nexus() {
        this.add((T) this);
    }

    public T add(T obj) {
        // Delegate to HeadAndTail
        return getHeadAndTail().add(obj);
    }

    /** @return a static for the class */
    protected abstract HeadAndTail getHeadAndTail();
}

/** Bundled into one Object for simplicity of API */
class HeadAndTail> {
    T head = null;
    T tail = null;
    int num = 0;

    public T add(T obj) {
        obj.next = null;
        if (num++ == 0)
            head = tail = obj;
        else
            tail = tail.next = obj;

        return obj;
    }
}

class ConcreteNexus extends Nexus {
    // This is the static object all instances will return from the method
    private static HeadAndTail headAndTail = new HeadAndTail();

    protected HeadAndTail getHeadAndTail() {
        return headAndTail; // return the static
    }
}