20 Immutable Interview Questions and Answers

If you’re interviewing for a position that involves working with Immutable, then you’re likely to encounter questions about the topic. Immutable is a tool that allows developers to create and manage immutable infrastructure. It is becoming increasingly popular, so it’s important to be familiar with the basics. In this article, we’ll review some of the most common Immutable interview questions and how you should answer them.

Immutable Interview Questions and Answers

Here are 20 commonly asked Immutable interview questions and answers to prepare you for your interview:

1. What is an immutable object?

An immutable object is an object whose state cannot be modified after it is created. Immutable objects are often used in concurrent programming to ensure that multiple threads can access an object without having to worry about the object’s state being modified by another thread.

2. Can you give me some examples of immutable objects in programming languages?

In general, immutable objects are those that cannot be changed after they have been created. In Java, for example, some of the immutable objects include the primitive types (such as int and char), as well as the String and BigInteger classes. In Python, meanwhile, some of the immutable objects include the int, float, bool, str, tuple, and frozenset types.

3. How can you make a class immutable in Java?

There are a few different ways to make a class immutable in Java. The most common way is to make all of the fields in the class final. This means that once the fields are set, they can never be changed. Another way to make a class immutable is to make the class itself final. This means that the class can never be extended or subclassed. Finally, you can also make all of the methods in the class final. This means that they can never be overridden.

4. Is it possible to make an existing mutable class immutable in Java? If yes, then how?

Yes, it is possible to make an existing mutable class immutable in Java. To do so, you would need to make all of the fields in the class final, and make sure that the class cannot be subclassed. Additionally, you would need to make sure that any methods in the class that could potentially modify the state of the object are either made private or removed entirely.

5. How does immutability affect the performance and efficiency of your application?

Immutability can affect the performance and efficiency of your application in a number of ways. For one, it can help to avoid concurrency issues by ensuring that data is not modified while it is being accessed by multiple threads. Additionally, immutable data structures can be more easily cached and reused, which can improve performance by avoiding the need to recalculate or recreate them each time they are needed. Finally, immutable data can also help to improve memory usage by avoiding the need to duplicate data that is not going to be changed.

6. What are the differences between mutable and immutable objects?

Mutable objects are those which can be changed after they are created, while immutable objects cannot be changed after they are created. This means that if you have a mutable object, you can modify it in place without creating a new object, but if you have an immutable object, you will need to create a new object if you want to change it in any way. Mutable objects are generally more convenient to work with, but immutable objects can be more efficient and easier to reason about.

7. What do you know about string immutability?

String immutability is a concept in computer programming that refers to the inability of a string to be changed once it has been created. This is different from other data types which can be changed (or mutated) after they have been created. The main advantage of string immutability is that it helps to prevent data corruption and can make code easier to reason about.

8. Why should we use immutable data structures?

Immutable data structures are those that cannot be changed after they have been created. This means that they are thread-safe, and can be shared between different threads without the risk of data corruption. Additionally, immutable data structures are often more efficient than their mutable counterparts, since they don’t need to waste time and resources making copies every time they are modified.

9. What’s the difference between value semantics and reference semantics?

Value semantics mean that when you assign a value to a variable, a copy of that value is made. Reference semantics mean that when you assign a value to a variable, a reference to that value is made.

10. What is a frozen set? When would you use one?

A frozen set is an immutable set, meaning that once it is created, it cannot be changed. This can be useful if you need to ensure that a set of values will not be modified, for example in a database or cache.

11. Is it possible to update a tuple in Python?

No, it is not possible to update a tuple in Python. Tuples are immutable, meaning that they cannot be changed after they are created. If you need to update the values in a tuple, you will need to create a new tuple with the updated values.

12. Can you explain what pure functions are? How do they relate to immutable objects?

Pure functions are functions that always return the same output for a given input, and have no side effects. This means that they do not modify any global state or anything outside of their own scope. Immutable objects are objects that cannot be modified once they are created. Pure functions can only operate on immutable objects, because if they tried to modify a mutable object, it would cause the function to no longer be pure.

13. What is the advantage of using immutable classes over mutable ones?

The advantage of using immutable classes is that they are much more secure. With an immutable class, you can be sure that no one is going to change the state of your objects without your permission. This is because once an immutable object is created, it cannot be modified. This means that any attempts to change its state will simply result in a new object being created, rather than the original object being modified. This can help to prevent a lot of potential security issues.

14. Which one is better – using immutable objects or concurrency control for thread safety?

There is no definitive answer to this question, as it depends on the specific situation. If you are using immutable objects, then you can be sure that the state of those objects will not change, even if multiple threads are accessing them. This can simplify your code and make it easier to reason about. However, if you need to be able to update the state of an object, then you will need to use concurrency control to ensure that only one thread can access the object at a time.

15. What happens if you try to change an immutable variable after it has been initialized? Will it create a new instance or will it throw an error?

An immutable variable cannot be changed after it has been initialized. If you try to change the value of an immutable variable, it will throw an error.

16. Are dictionaries mutable or immutable in Python?

Dictionaries are mutable in Python, which means that they can be changed after they are created.

17. What is the point of having immutable values?

The point of having immutable values is to ensure that data cannot be changed once it has been set. This is important in situations where data needs to be consistent and reliable, such as in financial transactions. Immutable values also make it easier to write correct code, since you can be sure that the data will not be changed unexpectedly.

18. What is the best way to avoid mutating state in JavaScript?

The best way to avoid mutating state in JavaScript is to use immutable data structures. Immutable data structures are data structures that cannot be changed after they have been created. This means that you can never accidentally mutate state when using an immutable data structure.

19. Is there any relationship between hash tables and immutable values?

Yes, immutable values can be used as keys in hash tables. This is because the key-value pairs in a hash table are stored based on the hash code of the key, and immutable values always have the same hash code.

20. What are some advantages of using immutable variables in Scala?

Some advantages of using immutable variables in Scala are that they are thread-safe, they can’t be modified after they are created, and they can be easily shared between different threads.