Different reference types in Java can be confusing

Strong Soft Weak and Phantom References

What does it mean?

PhantomlyReferenced.java

import java.lang.ref.PhantomReference;
import java.lang.ref.ReferenceQueue;

public class PhantomlyReferenced {
  
  private ReferenceQueue<Object> queue = new ReferenceQueue<>();
  private PhantomReference<Object> value = new PhantomReference<Object>(new Object(), queue);
  
  public Object getValue() {
    // always returns null
    return value.get();
  }
}

SoftlyReferenced.java

import java.lang.ref.SoftReference;

public class SoftlyReferenced {
  
  private SoftReference<Object> value = new SoftReference<Object>(new Object());
  
  public Object getValue() {
    return value.get();
  }

}

WeaklyReferenced.java

import java.lang.ref.WeakReference;

public class WeaklyReferenced {
  
  private WeakReference<Object> value = new WeakReference<Object>(new Object());
  
  public Object getValue() { 
    return value.get(); 
  }

}