LinkedHashMap and LinkedHashSet in Java

In this article, we will learn the LinkedHashMap and LinkedHashSet in Java.

LinkedHashMap

Hash table and linked list implementation of the Map interface, with predictable iteration order.

Example

Let us see an example ?

import java.util.*;
public class Demo {
   public static void main(String args[]){
      LinkedHashMap<Integer, String> my_set;
      my_set = new LinkedHashMap<Integer, String>();
      my_set.put(67, "Joe");
      my_set.put(90, "Dev");
      my_set.put(null, "Nate");
      my_set.put(68, "Sara");
      my_set.put(69, "Amal");
      my_set.put(null, "Jake");
      my_set.put(69, "Ral");
      my_set.entrySet().stream().forEach((m) ->{
         System.out.println(m.getKey() + " " + m.getValue());
      });
   }
}

Output

67 Joe
90 Dev
null Jake
68 Sara
69 Ral

A class named Demo contains the main function, where an instance of the LinkedHashMap is created. Elements are added into this hash map using the put() method, in the "integer, string'" format. A forEach loop is used to iterate over the hash map and elements are displayed on the console.

LinkedHashSet

Hash table and linked list implementation of the Set interface, with predictable iteration order.

Example

Let us see an example ?

import java.util.*;
public class Demo {
   public static void main(String args[]){
      LinkedHashSet<String> my_set;
      my_set = new LinkedHashSet<String>();
      my_set.add("Joe");
      my_set.add("Dev");
      my_set.add("Nate");
      my_set.add("Sara");
      my_set.add("Amal");
      my_set.add("Jake");
      my_set.add("Ral");
      Iterator<String> my_itr = my_set.iterator();
      while (my_itr.hasNext()){
         System.out.println(my_itr.next());
      }
   }
}

Output

Joe
Dev
Nate
Sara
Amal
Jake
Ral

A class named Demo contains the main function, where an instance of the LinkedHashSet is created. Elements are added into this LinkedHashSet using the add() method. An iterator is defined that can be used to iterate over the hash set elements. These elements are displayed on the console.