Created: 07 February 2023

Topics and a list of the 20 most effective Java programming interview questions

You can anticipate that during a Java programming interview, your knowledge of the Java programming language and its ideas will be assessed, along with your aptitude for using Java to resolve programming issues.

You may be tested on a variety of subjects, such as:

- Java fundamentals like polymorphism, encapsulation, inheritance, and abstraction.
- OOP (Object-Oriented Programming) design patterns and principles.
- understanding of algorithms and data structures, including how to use Java to implement them.
- knowledge of Java API classes and libraries like java.util, java.io, java.lang, and others
- understanding of Java's concurrency and multi-threading.
- understanding of Java debugging and exception handling.
- knowledge of well-known Java frameworks, including Spring, Hibernate, and others.
- knowledge of databases and SQL, as well as how to use Java to interact with databases.
- the capacity to write readable, efficient, and maintainable code.
- good knowledge of testing and debugging in the software development process.

20 frequently asked questions about Java programming are listed below:

1. What distinguishes procedural programming from object-oriented programming?
2. What distinguishes an abstract class from an interface?
3. How does a JVM operate and what is it?
4. What distinguishes heap memory from stack memory?
5. What distinguishes checked from unchecked exceptions, please?
6. How do you make a singleton class in Java? What is it used for?
7. What distinguishes equals() and == from one another?
8. Can you describe the distinction between a Java HashMap and Hashtable?
9. How are processes and threads different from one another?
10. Can you explain the last Java keyword?
11. What distinguishes a Java static inner class from a non-static inner class?
12. What distinguishes an ArrayList from a LinkedList in Java?
13. What distinguishes a Java while loop from a do-while loop, exactly?
14. What distinguishes Java's wait() and sleep() methods from one another?
15. Can you describe the distinction between a Java class and object?
16. In Java, what distinguishes a function Object() { [native code] } from a method?
17. Can you clarify the distinction between Java's static and dynamic binding?
18. What is polymorphism and how does Java use it?
19. Can you clarify the distinction between Java's deep and shallow copies?
20. Can you describe the distinction between a Java object and a reference?

Both theoretical and practical interview questions, where you'll have to explain ideas and write Java code to address problems with programming, may be present.

During the interview, be prepared to be asked to describe your thought process and the logic behind your solution.

Frequently Asked Questions (FAQs)

• 1. What is Java programming used for?
  Java is a very flexible language that can be used for anything from server-side applications to games to desktop and mobile applications. The majority of Android apps, business applications, and major projects are written in Java.
• 2. What is the difference between JDK and JRE?
  The Java Development Kit (JDK) is a set of tools for creating Java-based programmes. It comes with the Java compiler, the Java runtime environment, and other tools necessary for developing in Java. Conversely, a JRE (Java Runtime Environment) is a runtime environment needed to run Java programmes. Java SE Runtime Environment (JRE) and supporting libraries are included.
• 3. What is the difference between an interface and an abstract class?
  Java's interfaces and abstract classes both serve the same purpose of achieving abstraction, but they do it in different ways. A contract or set of guidelines that a class must adhere to is defined by its interface. Method signatures and constants are all that are present; no actual code is included. Conversely, an abstract class may include both abstract and non-abstract methods, as well as implementation code. In order to make use of an abstract class, a subclass must extend it.
• 4. What is the difference between a class and an object?
  Classes in Java are like blueprints or templates; they specify how an object should be constructed and what methods it should implement. Basically, it lays out all the features and operations that an instance of that class will have. In contrast, an object is a dynamically produced instance of a class. Each instance of a class has its own unique value for each attribute and can execute any of the class's methods.
• 5. What is a static method in Java?
  A static method in Java is a method that is associated with the class itself, rather than any particular instance of the class. Without first generating an instance of the class, it can only work with static variables and other static methods. Use the class name followed by the method name to call a static method that was specified with the static keyword.