What types of references are there in Java?

In Java, there are several types of references that affect garbage collection and the lifecycle of objects:

• Strong Reference — a normal reference to an object. As long as strong references exist, the object will not be garbage collected.

• Soft Reference — an object with a soft reference is only removed when memory is low. Used for caching.

• Weak Reference — an object with a weak reference can be garbage collected during the next garbage collection cycle, even if weak references exist.

• Phantom Reference — used to track when an object is ready for garbage collection but not yet collected. Allows for additional actions after finalization.

Example of creating a weak reference:

import java.lang.ref.WeakReference;

String strong = new String("Hello");
WeakReference<String> weak = new WeakReference<>(strong);

strong = null; // now the object is only accessible through weak
// during garbage collection, the object may be collected