LinkedHashSet is an implementation of Set Abstract Data Type (ADT). It extends from the HashSet class which in-turn implements Set Interface. The difference between the LinkedHashSet and HashSet is the property of maintaining the element ordering. LinkedList is just a container holding sequence of elements. By definition, Set should not contain duplicate elements. This property need not hold good for the LinkedList ADT. When elements should be duplicated and the order has to be maintained, one should use LinkedHashSet.
Methods:
There are basically three standard ways to get an element from LinkedHashSet without changing it to a different data structure.
Implementation: Getting the First Element from LinkedHashSet
Method 1: By converting it to an array or List
Example
Java
// Java Program to Get the First Element from LinkedHashSet// by converting it to an array or List// Array is demonstrated below so do with List// Importing generic java packagesimport java.io.*;import java.lang.*;import java.util.*;// Classpublic class GFG { // Main driver method public static void main(String[] args) throws java.lang.Exception { // Creating a LinkedHashMap object // Declaring object of Integer type LinkedHashSet<Integer> hashSet = new LinkedHashSet<Integer>(); // Adding elements to LinkedHashMap hashSet.add(2); hashSet.add(1); hashSet.add(4); hashSet.add(6); hashSet.add(8); // Condition check using isEmpty() method which // holds // True till there is a single element in an object // is remaining False, when there is no object left // or if initially there was no element added if (!hashSet.isEmpty()) { // Converting the above Map to an array Integer arr[] = new Integer[hashSet.size()]; arr = hashSet.toArray(arr); // Accessing the first element by passing 0 // as an argument which by default // accesses and prints out first element System.out.println("First element: " + arr[0]); } }} |
First element: 2
Method 2: Using Iterators
Example
Java
// Java Program to Get the First Element from LinkedHashSet// Using Iterators// Importing generic java packagesimport java.util.*;import java.lang.*;import java.io.*;// Classpublic class GFG { // Main driver method public static void main(String[] args) throws java.lang.Exception { // Creating a LinkedHashMap LinkedHashSet<Integer> hashSet = new LinkedHashSet<Integer>(); // Adding elements to LinkedHashMap hashSet.add(1); hashSet.add(2); hashSet.add(3); hashSet.add(4); hashSet.add(5); // Iterator over LinkedHashMap Iterator<Integer> iter = hashSet.iterator(); if (iter != null && iter.hasNext()) { // Display the first element of Map using next() // ethod System.out.println( "First element in LinkedHashSet: " + iter.next()); } }} |
First element in LinkedHashSet: 1
Method 3: Using Streams
Example:
Java
// Java Program to Get the First Element from LinkedHashSet// Using Streams// Importing generic java packagesimport java.util.*;import java.lang.*;import java.io.*;// Classclass GFG { // Main driver method public static void main(String[] args) throws java.lang.Exception { // Creating a LinkedHashMap LinkedHashSet<Integer> hashSet = new LinkedHashSet<Integer>(); // Adding elements to LinkedHashMap hashSet.add(1); hashSet.add(2); hashSet.add(3); hashSet.add(4); hashSet.add(5); // Checking whether Map is empty or not if (hashSet.size() == 0) // Display message System.out.println("The Set is Empty!"); else { // Using stream() through findFirst() method // over the elements of LinkedHashMap int first = hashSet.stream().findFirst().get(); // Printing the first element of LinkedHashMap System.out.println( "First element in LinkedHashSet: " + first); } }} |
First element in LinkedHashSet: 1
