Java Collection Interview Questions

Complete Guide on LinkedHashMap in Java

Everything you need to know about LinkedHashMap in Java.

The red-black tree that is internally used for TreeMap

Learning collection classes are essential as they are heavily used while creating the real-world Application. There are a few important collection classes that I have already covered (HashMap, ConcurrentHashMap, TreeMap). This article is a continuation of that and we’ll deep dive into what, why, and how of the LinkedHashMap class.

What Is LinkedHashMap?

• LinkedHashMap is Hashtable and linked list implementation of the Map interface, with predictable iteration order.
• This implementation differs from HashMap in that, it maintains a doubly-linked list running through all of its entries. This linked list defines the iteration ordering, which is normally the order in which keys are inserted into the map (insertion order).
• Note that insertion order is not affected if a key is re-inserted into the map. (A key k is reinserted into a map m if m.put(k, v) is invoked when m.containsKey(k) would return true immediately before the invocation.)
• This implementation spares its clients from the unspecified, generally chaotic ordering provided by HashMap (and Hashtable)…