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Programming Concepts Intermediate

What is Immutable Object?

An object whose state cannot be modified after creation, providing thread safety and predictable behavior in concurrent systems.

Immutable objects, once created, cannot have their fields changed. Any modification creates a new object instead. This eliminates a class of bugs related to shared mutable state in concurrent programs — no locks are needed because the data cannot change. In Python, tuples and frozensets are immutable. In Java, Strings are immutable. Functional programming languages (Haskell, Clojure) default to immutability. Benefits include simpler reasoning about code, safe sharing between threads, reliable hash keys, and easier undo/redo implementations. The trade-off is potential memory overhead from creating new objects for every change, though structural sharing can mitigate this.

Related Terms

Race Condition
A bug that occurs when the behavior of software depends on the timing or order of uncontrolled events like thread scheduling.
Technical Debt
The implied cost of additional rework caused by choosing a quick solution now instead of a better approach that would take longer.
Unit Testing
Testing individual components or functions of a program in isolation to verify they work correctly.
Concurrency
The ability of a program to manage multiple tasks that can make progress during overlapping time periods.
Closure
A function that captures and retains access to variables from its enclosing scope, even after that scope has finished executing.
Refactoring
Restructuring existing code without changing its external behavior to improve readability, maintainability, and performance.
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