Java.util.LinkedHashMap Class

Introduction

The java.util.LinkedHashMap class is Hash table and Linked list implementation of the Map interface, with predictable iteration order.Following are the important points about LinkedHashMap:

• The class provides all of the optional Map operations, and permits null elements.
• The Iteration over a HashMap is likely to be more expensive.

Class declaration

Following is the declaration for java.util.LinkedHashMap class:

public class LinkedHashMap<K,V>
   extends HashMap<K,V>
   implements Map<K,V>

Parameters

Following is the parameter for java.util.LinkedHashMap class:

• K -- This is the type of keys maintained by this map.
• V -- This is the the type of mapped values.

Class constructors

S.N.	Constructor & Description
1	LinkedHashMap() This constructs an empty insertion-ordered LinkedHashMap instance with the default initial capacity (16) and load factor (0.75).
2	LinkedHashMap(int initialCapacity) This constructs an empty insertion-ordered LinkedHashMap instance with the specified initial capacity and a default load factor (0.75).
3	LinkedHashMap(int initialCapacity, float loadFactor) This constructs an empty insertion-ordered LinkedHashMap instance with the specified initial capacity and load factor.
4	LinkedHashMap(int initialCapacity, float loadFactor, boolean accessOrder) This constructs an empty LinkedHashMap instance with the specified initial capacity, load factor and ordering mode.
5	LinkedHashMap(Map<? extends K,? extends V> m) This constructs an insertion-ordered LinkedHashMap instance with the same mappings as the specified map.

Class methods

S.N.	Method & Description
1	void clear() This method removes all of the mappings from this map.
2	boolean containsValue(Object value) This method returns true if this map maps one or more keys to the specified value.
3	V get(Object key) This method returns the value to which the specified key is mapped, or null if this map contains no mapping for the key.
4	protected boolean removeEldestEntry(Map.Entry<K,V> eldest) This method returns true if this map should remove its eldest entry.

Methods inherited

This class inherits methods from the following classes:

• java.util.HashMap
• java.util.AbstarctMap
• java.util.Object
• java.util.Map