An Entry maintaining a key and a value. The value may be changed using the <tt>setValue</tt> method. This class facilitates the process of building custom map implementations. For example, it may be convenient to return arrays of <tt>SimpleEntry</tt> instances in method <tt>Map.entrySet().toArray</tt>.
An Entry maintaining an immutable key and value. This class does not support method <tt>setValue</tt>. This class may be convenient in methods that return thread-safe snapshots of key-value mappings.