Iterator Interface Example in Java

Introduction

Iterator Interface 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

An iterator for lists that allows the programmer to traverse the list in either direction, modify the list during iteration, and obtain the iterator’s current position in the list.

Syntax

ListIterator<variable-type> variable-name= list-name.listIterator();

Iterator Interface Example Program

import java.util.*;

public class IteratorExample {

    public static void main(String[] args) {
        List<String> locationsList = new ArrayList<String>();

        locationsList.add("Chennai");
        locationsList.add("Mumbai");
        locationsList.add("Hyderabad");
        locationsList.add("Lucknow");
        locationsList.add("Bangaluru");

        System.out.println("List is : " + locationsList);

        System.out.println("Printing list items using Iterator");

        ListIterator<String> locationsIterator = locationsList.listIterator();

        while (locationsIterator.hasNext()) {
            System.out.println(locationsIterator.next());
        }
    }
}

Sample Output

List is : [Chennai, Mumbai, Hyderabad, Lucknow, Bangaluru]
Printing list items using Iterator
Chennai
Mumbai
Hyderabad
Lucknow
Bangaluru

When to use

Use this iterator interface 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.*; imports a class used later in the program.

3. List<String> locationsList = new ArrayList<String>(); 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. ListIterator<String> locationsIterator = locationsList.listIterator(); updates a variable used in the calculation or output.

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

8. Compare your console output with the sample output for Iterator Interface 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.