Java.util.LinkedHashMap Class

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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

Sr.No. 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

Sr.No. 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
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