ReferenceExample.java

package com.example.reference;
import java.lang.ref.PhantomReference;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.SoftReference;
import java.lang.ref.WeakReference;
/*
 *  https://dzone.com/articles/java-different-types-of-references
 */
public class ReferenceExample {
       private String status ="Hi I am active";

       public static void main(String[] args) {
              ReferenceExample ex = new ReferenceExample();
              ex.strongReference();
              ex.softReference();
              ex.weakReference();
              try {
                     ex.phantomReference();
              } catch (InterruptedException e) {
                     // TODO Auto-generated catch block
                     e.printStackTrace();
              }
       }

       public String getStatus() {
              return status;
       }

       public void setStatus(String status) {
              this.status = status;
       }

       @Override
       public String toString() {
              return "ReferenceExample [status=" + status + "]";
       }

       public void strongReference()
       {
              ReferenceExample ex = new ReferenceExample();
              System.out.println(ex);
       }

       public void softReference()
       {
              SoftReference<ReferenceExample> ex = new SoftReference<ReferenceExample>(getRefrence());
              System.out.println("Soft refrence :: " + ex.get());
       }

       public void weakReference()
       {
              int counter=0;
              WeakReference<ReferenceExample> ex = new WeakReference<ReferenceExample>(getRefrence());
              while(ex.get()!=null)
              {
                     counter++;
                     System.gc();
                     System.out.println("Weak reference deleted  after:: " + counter + ex.get());
              }
       }

       public void phantomReference() throws InterruptedException
       {
              final ReferenceQueue queue = new ReferenceQueue();
              PhantomReference<ReferenceExample> ex = new PhantomReference<ReferenceExample>(getRefrence(),queue);
              System.gc();
              queue.remove();
              System.out.println("Phantom reference deleted  after");
       }

       private ReferenceExample getRefrence()
       {
              return new ReferenceExample();
       }
}