Top 10 JAVA Interview Questions and Answers

Authored By: Ankita Prajapati

JAVA is a widely used object-oriented programming language and software platform that runs on billions of devices. The journey of Software Development begins with JAVA and it consists of logics and programming to produce software solutions to any real problem.. You must understand the basics of JAVA to secure a job related to it. Read the top JAVA Interview Question and Answers.

Question 1: Why is JAVA a platform-independent language?

Answer: Because the compiler compiles the code and then converts it to platform-independent byte code that can be run on various platforms, the Java language was created in a way that it is independent of all hardware and software. The installation of a runtime environment (JRE) on the machine is the only prerequisite for that byte code to run.

Question 2: Why is JAVA not a pure object-oriented language?

Answer: Java is not a pure object-oriented language because it offers primitive data types such as bytes, booleans, chars, short ints, floats, long ints, and doubles.

Question 3: Difference between Heap and Stack memory in JAVA.

Answer: STACK MEMORY- The memory space allotted to each distinct program is known as stack memory. It was then corrected.

HEAP MEMORY- Heap memory is the piece of memory that was not allotted to the Java program but will be accessible to it when needed, often during the program’s runtime.

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Question 4: Can JAVA be said to be the complete object-oriented programming language?  

Answer: We can legitimately assert that Java is a full-featured object-oriented programming language. Because classes are the foundation of Java. And by making things, we may gain access to that. Additionally, if we consider that Java supports primitive data types like int, float, char, boolean, double, etc., then we can argue that it is not a fully object-oriented programming language. 

Question 5: How is JAVA different from C++?

Answer: Java is both a compiled and an interpreted language, whereas C++ is simply a compiled language.

Question 6: Pointers are used in C/C++. Why does JAVA not make use of pointers?  

Answer: Beginner programmers should avoid using pointers because they are fairly difficult. Java relies on writing simple code, therefore using pointers might be difficult. Potential faults can also be caused by pointer usage. Furthermore, the use of pointers compromises security since they allow users to directly access memory. Thus, the absence of pointers in Java provides a certain level of abstraction. Furthermore, the use of pointers may result in a delayed and inaccurate garbage collection process. Java uses references because, unlike pointers, they cannot be changed. 

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Question 7: What do you understand by an instance variable and a local variable? 

Answer: All methods in the class can access variables known as instance variables. They are stated both inside the class and outside the methods. These variables, which are inextricably linked to an object, characterize its characteristics. Local variables are variables that can only be accessed inside a block, function, or function Object() { [native code] }. The variable can only be used within the block scope.

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Question 8: What are the default values assigned to variables and instances in JAVA? 

Answer: Java doesn’t provide its variables any default values. Before using the value, it must first be initialized. Otherwise, a compilation error with the value (Variable might not be initialized). However, depending on the data type, the default value will be initialized by the default function Object() { [native code] } if we build the object. 

  1. It will be assigned to null if it is a reference. 
  2. If it is a number, it will assign a value of 0. 
  3. If the value is a Boolean, a false will be set to it.

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Question 9: What do you mean by data encapsulation? 

Answer: In Object-Oriented Programming, the idea of data encapsulation refers to the hiding of data properties and associated behaviors within a single unit. Guaranteeing that each object is independent of other objects by having its methods, properties, and functions, aids developers in adhering to the modularity principle when creating software. It serves the purpose of data hiding by being used to secure an object’s private properties.

Question 10: Tell us something about the JIT compiler.

Answer: JIT, or just-in-time, is a technique for enhancing run-time performance. It reduces the amount of time required for the code to compile by doing the task of compiling portions of byte code with identical functionality at the same time. The compiler merely converts source code into machine-readable code. But what makes the JIT compiler unique? Let’s examine its operation: With the aid of the java compiler, the Java source code (.java) is first converted to byte code (.class).

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