Set Value in Arraylist Example in Java

Introduction

Set Value in ArrayList 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 ArrayList is a non-syncronized class. It implements List Interface and inherits AbstractList class. It maintains insertion order.

Syntax

arrayList.set(index, value);

Set Value Example Program

import java.util.ArrayList;

public class SetValueExample {

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

        animalsArrayList.add("Lion");
        animalsArrayList.add("Tiger");
        animalsArrayList.add("Camel");
        animalsArrayList.add("Giraffee");
        animalsArrayList.add("Deer");
        animalsArrayList.add("Bear");
        animalsArrayList.add("Cheetah");
        animalsArrayList.add("Hyena");

        System.out.println("Initial ArrayList is : " + animalsArrayList);// Printing the arraylist
        animalsArrayList.set(6, "Leopard"); //Setting animal - leopard at position 6 (or) Replacing Cheetah by Leopard at position 6
        System.out.println("ArrayList after setting/replacing element at position 6 is : " + animalsArrayList);
    }
}

Sample Output

Initial ArrayList is : [Lion, Tiger, Camel, Giraffee, Deer, Bear, Cheetah, Hyena]
ArrayList after setting/replacing element at position 6 is : [Lion, Tiger, Camel, Giraffee, Deer, Bear, Leopard, Hyena]

When to use

Use this set value in arraylist 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.ArrayList; imports a class used later in the program.

3. ArrayList<String> animalsArrayList = 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. Compare your console output with the sample output for Set Value in ArrayList 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.