java.lang.ref.Reference Class in Java

// Java program to illustrate working of Reference Class
import java.lang.ref.Reference;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.SoftReference;
class Gfg {
}

public class GFG {

    public static void main(String[] args)
    {
        // Strong Reference
        Gfg g = new Gfg();

        ReferenceQueue<Gfg> q = new ReferenceQueue<Gfg>();

        // Creating Soft Reference to Gfg-type object to
        // which 'g' is also pointing and registering it
        // with q
        Reference<Gfg> softref
            = new SoftReference<Gfg>(g, q);

        g = softref.get();
        System.out.println(g.toString());
        // enqueue softref to its registered queue i.e q

        if (softref.enqueue()) {
            System.out.println(
                "Object successfully enqueued");
        }
        else {
            System.out.println("Object not enqueued");
        }

        // checking if softref is enqueued or not
        if (softref.isEnqueued()) {
            System.out.println("Object is enqueued");
        }
        else {
            System.out.println("Object not enqueued");
        }

        // clearing this reference object
        softref.clear();

        System.out.println("Object cleared");

        // trying to enqueue after clearing
        if (softref.enqueue()) {
            System.out.println(
                "Object successfully enqueued");
        }
        else {
            System.out.println("Object not enqueued");
        }
    }
}