JAVA Syllabus

What do you mean by mutable and immutable objects?

In programming, objects can be classified as either mutable or immutable based on whether their state (data) can be changed after they are created. Let's explain the concepts of mutable and immutable objects:

  1. Mutable Objects: Mutable objects are objects whose state can be modified or changed after they are created. This means you can alter their data, add new elements, remove elements, or update their properties without creating a completely new instance of the object. In other words, you can change the object's internal state without creating a new memory location for it.

Examples of mutable objects in many programming languages include lists, arrays, sets, dictionaries, and custom objects/classes that allow modification of their fields/properties.

Here's an example of a mutable list in Python:

mutable_list = [1, 2, 3]
mutable_list.append(4)   # Modifies the list by adding a new element
mutable_list[0] = 100    # Modifies the first element of the list
  1. Immutable Objects: Immutable objects, on the other hand, are objects whose state cannot be changed after they are created. Once an immutable object is created, its data cannot be modified or updated. If you want to change the data, you need to create a new instance of the object with the updated value. This design choice is often made for safety, thread-safety, and consistency reasons.

Examples of immutable objects include strings, numbers (e.g., integers, floating-point numbers), tuples, and some built-in types like frozensets (an immutable version of a set).

Here's an example of an immutable string in Python:

immutable_string = "Hello"
# The following line will create a new string object rather than modifying the existing one
new_string = immutable_string + " World"

Advantages of Immutable Objects:

  • Thread Safety: Immutable objects are inherently thread-safe since they cannot be changed after creation, reducing the risk of concurrency-related issues.
  • Hashability: Immutable objects can be used as keys in dictionaries or elements in sets because their hash value remains constant throughout their lifetime.

Disadvantages of Immutable Objects:

  • Performance Overhead: Creating a new object every time the data needs to change can lead to additional memory and performance overhead, especially for large objects.
  • Complexity: Immutable objects might require creating new instances more frequently, which can make the code more complex.

In summary, mutable objects allow changes to their state after creation, while immutable objects do not allow modifications and require creating new instances to change their data. The choice between mutable and immutable objects depends on the specific requirements of a program and the desired trade-offs between performance, safety, and code simplicity.

25/07/2023, 11:32 am Read : 65 times