LinkedHashMap and LinkedHashSet in Java Last Updated : 21 Feb, 2023 Comments Improve Suggest changes Like Article Like Report The LinkedHashMap is just like HashMap with an additional feature of maintaining an order of elements inserted into it. HashMap provided the advantage of quick insertion, search, and deletion but it never maintained the track and order of insertion which the LinkedHashMap provides where the elements can be accessed in their insertion order. Example: Java // Java program to demonstrate // working of LinkedHashMap import java.util.*; class LinkedHashMapExample { public static void main(String args[]) { // create an instance of LinkedHashMap LinkedHashMap<Integer, String> lhm; lhm = new LinkedHashMap<Integer, String>(); // insert element in LinkedHashMap lhm.put(100, "Amit"); // insert first null key lhm.put(null, "Ajay"); lhm.put(101, "Vijay"); lhm.put(102, "Rahul"); // insert second null key // which replace first null key value lhm.put(null, "Anuj"); // insert duplicate // which replace first 102 key value lhm.put(102, "Saurav"); // iterate and print the key/value pairs lhm.entrySet().stream().forEach((m) -> { System.out.println(m.getKey() + " " + m.getValue()); }); } } Output100 Amit null Anuj 101 Vijay 102 Saurav The LinkedHashSet is an ordered version of HashSet that maintains a doubly-linked List across all elements. When the iteration order is needed to be maintained this class is used. When iterating through a HashSet the order is unpredictable, while a LinkedHashSet lets us iterate through the elements in the order in which they were inserted. When cycling through LinkedHashSet using an iterator, the elements will be returned in the order in which they were inserted. Example: Java // Java program to demonstrate // working of LinkedHashSet import java.util.*; class LinkedHashSetExample { public static void main(String args[]) { // create an instance of LinkedHashSet LinkedHashSet<String> lhs = new LinkedHashSet<String>(); // insert element in LinkedHashMap lhs.add("Amit"); // insert first null key lhs.add(null); lhs.add("Vijay"); lhs.add("Rahul"); // insert second null key // which replace first null key value lhs.add(null); // insert duplicate lhs.add("Vijay"); // create an iterator // iterate and print the elements Iterator<String> itr = lhs.iterator(); while (itr.hasNext()) { System.out.println(itr.next()); } } } OutputAmit null Vijay Rahul The Hierarchy of LinkedHashMap and LinkedHashSet Similarities between LinkedHashMap and LinkedHashSetProperty LinkedHashMap and LinkedHashSet OrderBoth LinkedHashMap and LinkedHashSet maintain the insertion order. Elements get sorted in the same sequence in which they have been added.SynchronizedBoth are not synchronized and must be synchronized externally.DuplicatesLinkedHashMap does a mapping of keys to values so it doesn't have duplicates and LinkedHashSet simply stores a collection of things with no duplicates.MemoryKeeping the insertion order in both LinkedHashmap and LinkedHashset have additional associated costs, both in terms of spending additional CPU cycles and needing more memory.Differences between LinkedHashMap and LinkedHashSetProperty LinkedHashMap LinkedHashSet Declaration The default constructor declaration is : LinkedHashMap lhm = new LinkedHashMap(); The default constructor declaration is : LinkedHashSet hs = new LinkedHashSet(); Class Declarationpublic class LinkedHashMap<K, V> extends HashMap<K, V> implements Map<K, V>public class LinkedHashSet<E> extends HashSet<E> implements Set<E>, Cloneable, SerializableConstructor The LinkedHashMap accepts five types of constructors: LinkedHashMap()LinkedHashMap(int initialCapacity)LinkedHashMap(int initialCapacity, float fillRatio)LinkedHashMap(int initialCapacity, float fillRatio, boolean Order)LinkedHashMap(Map<? extends K,? extends V> m) The LinkedHashSet accepts four types of constructors: LinkedHashSet()LinkedHashSet(Collection<? extends E> C)LinkedHashSet(int initialCapacity)LinkedHashSet(int initialCapacity, float fillRatio)OperationLinkedHashMap does a mapping of keys to values.LinkedHashSet simply stores a collection of things.ReplacementLinkedHashMap replaces the value with a duplicate key.LinkedHashSet not change the original value.Null ObjectLinkedHashMap has elements in key-value pairs so have only one null key and multiple null values.LinkedHashSet simply stores a collection of things with one null value. Comment More infoAdvertise with us Next Article Design LRU Cache R rajput-ji Follow Improve Article Tags : Java Technical Scripter Difference Between Technical Scripter 2018 Java-LinkedHashMap java-LinkedHashSet +2 More Practice Tags : Java Similar Reads Java LinkedHashMap LinkedHashMap in Java implements the Map interface of the Collections Framework. It stores key-value pairs while maintaining the insertion order of the entries. It maintains the order in which elements are added.Stores unique key-value pairs.Maintains insertion order.Allows one null key and multiple 7 min read Java LinkedHashMap clear() Method The clear() method in Java is a built-in method of the java.util.LinkedHashMap class. This method is used to remove all the key-value mappings from a LinkedHashMap. After invoking this method, the map becomes empty.This method is very helpful when we want to reuse an existing map object without crea 2 min read LinkedHashMap containsKey() Method in Java with Examples The java.util.LinkedHashMap.containsKey() method is used to check whether a particular key is being mapped into the LinkedHashMap or not. It takes the key element as a parameter and returns True if that element is mapped in the map.Syntax: Linked_Hash_Map.containsKey(key_element) Parameters: The met 2 min read LinkedHashMap get() Method in Java with Examples In Java, get() method of LinkedHashMap class is used to retrieve or fetch the value mapped by a particular key mentioned in the parameter. It returns NULL when the map contains no such mapping for the key. --> java.util Package --> LinkedHashMap Class --> get() Method Syntax: Linked_Hash_Ma 2 min read LinkedHashMap removeEldestEntry() Method in Java The java.util.LinkedHashMap.removeEldestEntry() method in Java is used keep a track of whether the map removes any eldest entry from the map. So each time a new element is added to the LinkedHashMap, the eldest entry is removed from the map. This method is generally invoked after the addition of the 3 min read LinkedHashMap and LinkedHashSet in Java The LinkedHashMap is just like HashMap with an additional feature of maintaining an order of elements inserted into it. HashMap provided the advantage of quick insertion, search, and deletion but it never maintained the track and order of insertion which the LinkedHashMap provides where the elements 3 min read Design LRU Cache Design a data structure for LRU Cache. It should support the following operations: get and put.get(key) - Returns the value of the given key if it exists in the cache; otherwise, returns -1.put(key, value) - Inserts or updates the key-value pair in the cache. If the cache reaches capacity, remove th 5 min read Hashing in Java In hashing there is a hash function that maps keys to some values. But these hashing function may lead to collision that is two or more keys are mapped to same value. Chain hashing avoids collision. The idea is to make each cell of hash table point to a linked list of records that have same hash fun 6 min read Differences between TreeMap, HashMap and LinkedHashMap in Java Prerequisite: HashMap and TreeMap in Java TreeMap, HashMap and LinkedHashMap: What's Similar? All offer a key->value map and a way to iterate through the keys. The most important distinction between these classes is the time guarantees and the ordering of the keys.All three classes HashMap, TreeM 5 min read Like