Linked Hashset Example in Java

Introduction

Linked HashSet is a classic Java console program that demonstrates the concept with complete source code and sample output. The Collections Framework provides ArrayList, HashMap, HashSet and related data structures.

This tutorial walks through the program line by line, explains how the logic works, and highlights best practices you can apply in your own code.

Definition

HashSet uses a hash table. More specifically, it uses a java.util.HashMap to store the hashes and elements and to prevent duplicates. java.util.LinkedHashSet extends this by creating a doubly linked list that links all of the elements by their insertion order. This ensures that the iteration order over the set is predictable.

Syntax

LinkedHashSet Variable_name = new LinkedHashSet();

Linked HashSet Example Program

import java.util.LinkedHashSet;

public class LinkedHashSetDemo {
    public static void main(String a[]){
        LinkedHashSet lh = new LinkedHashSet();
        lh.add("Monday");
        lh.add("Tuesday");
        lh.add("Wednesday");
		lh.add("Thursday");
		lh.add("Friday");
		lh.add("Saturday");
		lh.add("Sunday");
        System.out.println(lh);
        System.out.println("Size of LinkedHashSet: "+lh.size());
        System.out.println("Is LinkedHashSet empty? : "+lh.isEmpty());
    }
}

Sample Output

[first, second, third]
LinkedHashSet size: 7
Is LinkedHashSet empty? : false

When to use

Use this linked hashset example when learning or revising core Java syntax.

How it works

1. Execution begins in the main method — the JVM calls this method when you run the class.

2. import java.util.LinkedHashSet; imports a class used later in the program.

3. LinkedHashSet lh = new LinkedHashSet(); updates a variable used in the calculation or output.

4. A println / print call writes text to the console — part of the sample output below.

5. A println / print call writes text to the console — part of the sample output below.

6. A println / print call writes text to the console — part of the sample output below.

7. Compare your console output with the sample output for Linked HashSet to confirm the program behaves correctly.

Best Practices

• Use meaningful variable and class names that describe their purpose.
• Compile and run the program locally — modify values to see how output changes.
• Read compiler errors carefully; they usually point to the exact line to fix.

Common Mistakes

• Copying code without understanding each line — practice by changing one statement at a time.
• Mismatching the public class name and the .java filename.
• Forgetting semicolons at the end of statements.