What Are Immutable Variables And Objects?

Table of contents

• Why is this useful?
• Examples
• Immutable Objects in Object-Oriented Programming

In programming, immutability means that once a variable [→] or object is created, its value cannot be changed. If you need a different value, you must create a new variable or object instead of modifying the existing one.

Why is this useful?

• Predictability – Since immutable variables never change by other developers or the program, their values stay the same throughout the program, making the code more predictable.
• Thread Safety – Immutable objects are safe to use in multi-threaded programs because they can't be modified unexpectedly.

Examples

In many programming languages, you can create immutable variables using special keywords.

Example in JavaScript (using const):

✅ Wrap📋
01: const name = "Ama";
02: name = "Kwesi"; // Error

Example in Python (using tuples):

✅ Wrap📋
01: coordinates = (10, 20)
02: coordinates[0] = 30  # Error: TypeError: 'tuple' object does not support item assignment

Immutable Objects in Object-Oriented Programming

In object-oriented languages, immutable objects can be created so that their internal state cannot change after instantiation.

Example in Java

✅ Wrap📋
01: final class Person {
02:     private final String name; // final keyword ensures immutability
03: 
04:     public Person(String name) {
05:         this.name = name;
06:     }
07: 
08:     public String getName() {
09:         return name;
10:     }
11: }

Once a Person object is created, the name field cannot be changed.

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