Java is one of the most popular programming languages used in software development and campus placements. For students preparing for technical interviews, understanding Java fundamentals and practicing coding problems is essential.
Here are 20 important Java interview questions every student should practice.
1. What is Java?
Java is a high-level, object-oriented programming language designed to be platform independent.
2. What is the difference between JDK, JRE, and JVM?
- JDK – Used to develop Java applications.
- JRE – Provides the environment to run Java applications.
- JVM – Executes Java bytecode.
3. What are the four pillars of OOP?
The four pillars of Object-Oriented Programming are:
- Encapsulation
- Inheritance
- Polymorphism
- Abstraction
4. What is a class?
A class is a blueprint or template used to create objects.
5. What is an object?
An object is an instance of a class that represents a real-world entity.
6. What is inheritance?
Inheritance allows a class to acquire properties and methods from another class.
7. What is method overloading?
Method overloading means defining multiple methods with the same name but different parameters.
8. What is method overriding?
Method overriding occurs when a child class provides its own implementation of a method inherited from its parent class.
9. What is the difference between == and .equals()?
== is generally used to compare references, while .equals() is used to compare the content of objects when properly overridden.
10. Why is String immutable in Java?
A String object cannot be changed after it is created. This makes strings secure and suitable for use in situations such as string pooling and hash-based collections.
11. What is an array?
An array stores multiple elements of the same data type in a fixed-size structure.
12. What is an exception?
An exception is an unexpected event that interrupts the normal flow of program execution.
13. What is the difference between ArrayList and LinkedList?
ArrayList is generally better for random access, while LinkedList can be useful for frequent insertions and deletions.
14. What is HashMap?
HashMap stores data in the form of key-value pairs.
Example:
HashMap<Integer, String> map = new HashMap<>();
15. What is HashSet?
HashSet stores unique elements and does not allow duplicate values.
16. What is a constructor?
A constructor is a special member used to initialize an object when it is created.
17. What is the static keyword?
The static keyword is used for members that belong to the class rather than individual objects.
18. What is multithreading?
Multithreading allows multiple threads to execute concurrently within a program.
19. What is garbage collection?
Garbage collection automatically removes objects that are no longer reachable and helps free memory.
20. What are some common Java coding problems?
Students should practice coding problems such as:
- Prime Number
- Palindrome
- Reverse a Number
- Sum of Digits
- Largest Element in an Array
- Remove Duplicates
- Sorting an Array
- Two Sum
Practice with Ti10 🚀
Learning Java becomes more effective when you combine theory with regular coding practice.
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Whether you are preparing for campus placements, technical interviews, or programming assessments, consistent practice can help you become a better programmer.
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Keep learning, keep coding, and prepare yourself for your next technical interview.
Happy Coding! 🚀
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