LinkedHashMap lhmap = new LinkedHashMap() // Generic formĢ. The general syntax to construct default LinkedHashMap object is as follows: LinkedHashMap lhmap = new LinkedHashMap() It constructs an empty insertion-ordered LinkedHashMap object with the default initial capacity 16 and load factor 0.75. LinkedHashMap(): This constructor is used to create a default LinkedHashMap object. Java LinkedHashMap class has the following constructors. The default initial capacity of LinkedHashMap class is 16 with a load factor of 0.75. That is, multiple threads can access the same LinkedHashMap object simultaneously.Ħ. LinkedHashMap in Java is non synchronized. LinkedHashMap allows only one null key but can have multiple null values.ĥ. The entries in Java LinkedHashMap can be retrieved either in the order in which they were inserted into the map (known as insertion order) or in the order in which they were last accessed, from least to most recently accessed.ģ. Java LinkedHashMap maintains the insertion order. The underlying data structure of LinkedHashMap is HashTable and LinkedList.Ģ. There are several features of LinkedHashMap in Java that should keep in mind. Here, K defines the type of keys, and V defines the type of values. LinkedHashMap is a generic class that is present in package. The hierarchy diagram of LinkedHashMap is shown in the below figure. That is, LinkedHashMap class extends the HashMap class and implements Map interface. LinkedHashMap implementation in Java is a subclass of HashMap class. HashMap was introduced in Java 1.2 version whereas, LinkedHashMap was introduced in Java 1.4 version. But in the case of LinkedHashMap, the insertion order of elements is preserved because it is based on the Key insertion order, that is, the order in which keys are inserted in the map.ģ.

Insertion order is not preserved in the HashMap because it is based on the hashCode of Key. The underlying data structure of HashMap is HashTable whereas, the underlying data structure of LinkedHashMap is HashTable and LinkedList (Hybrid data structure).Ģ. It is exactly the same as HashMap (including constructors and methods) except for the following differences:ġ. LinkedHashMap in Java was added in JDK 1.4 version. Java LinkedHashMap class extends the HashMap class with a linked-list implementation that supports an ordering of the entries in the map. It stores entries using a doubly-linked list. LinkedHashMap in Java is a concrete class that is HashTable and LinkedList implementation of Map interface.

Linked hashmap