Understanding WeakHashMap, IdentityHashMap, and EnumMap in Java

source : javamadesoeasy.com

Java provides several specialized Map implementations to cater to different use cases. Among these are WeakHashMap, IdentityHashMap, and EnumMap. This article delves into these three map implementations, highlighting their unique characteristics, use cases, and how to use them effectively in your Java applications.

WeakHashMap

WeakHashMap is a Map implementation based on weak references. A weak reference is a reference that does not prevent its referent from being made eligible for garbage collection. This means that the entries in a WeakHashMap can be garbage collected when their keys are no longer in use elsewhere in the program.

Characteristics:

• Entries are garbage collected when the keys are weakly reachable.
• Suitable for caching where memory-sensitive entries are desired.
• Not thread-safe. Use Collections.synchronizedMap for synchronized access.

Use Case:

WeakHashMap is ideal for scenarios where you want to hold metadata or cache values that can be discarded when memory is low, without needing explicit removal of entries.

Example:

import java.util.Map;
import java.util.WeakHashMap;

public class…