Understanding Mutable vs. Immutable Objects in Programming

In programming, particularly in languages like Java, Python, and JavaScript, the concepts of mutable and immutable refer to whether an object can be changed after it is created. Understanding these concepts is crucial for effective data management and application design.

Mutable Objects

Definition

Mutable objects are those whose state or value can be changed after they are created.

Characteristics

• Modifiable Attributes: You can modify their attributes, or add/remove elements.
• In-Place Operations: Operations that change the object do not create a new instance; instead, they alter the existing one.

Examples

• Java: ArrayList, HashMap, and StringBuilder are mutable.

List<String> list = new ArrayList<>();
list.add("Hello"); // The list is modified in place.

Immutable Objects

Definition

Immutable objects are those whose state or value cannot be changed after they are created.

Characteristics

• New Object Creation: Any modification results in the creation of a new object.
• Thread-Safe: They are inherently thread-safe since their state cannot be changed.

Examples