The Top 15 Java Interview Questions

by Vikas Yadav marketing

The Top Java Interview Questions

Do you want to ace the Java interview? Would you like to clear the interview with a good score and want to explore this great career opportunity?

Go through the below mentioned interview questions sorted to give you the best learning aid.

What makes Java platform-independent?

Java is the only language that works on the principle of writing once and running everywhere. It means that once the program is written in Java and compiled into byte code, it can easily be made to run on any Java virtual machine. Once a code is compiled, it can easily be made to run on any JVM, irrespective of the different operating systems and hardware.

Why is Java not a pure object-oriented language?

Java is not a pure object-oriented language as it supports primitive data types such as Boolean, char, short, int, float, long, and double.

Explain the concepts of JRE, JDK, and JVM?

The JRE is a Java runtime environment that includes the Java virtual machine and the standard Java APIs. It contains enough capacity to execute a Java application.

JDK stands for Java Development Kit, and it includes tools such as JRE and a Java compiler.

The JVM, or Java Virtual Machine, is an implementation of a specification that details the expected behaviour of a JVM.

What is the difference between heap and stack memory in Java?

Stack memory is the fixed memory that is assigned to every individual program, while heap memory is the portion of the memory that is made available for the Java program only when it is required.

How does Java utilize heap and stack memory?

Whenever a Java program is written, all the variables, methods, etc. are stored in stack memory, while when there is a need for any object to be included while allocating the space during a program, heap memory is used.

How is Java different from C++?

Java is a compiled and an interpreted language, while C++ is just a compiled language. Java programs are machine independent, while C++ programs run only on the machines for which they are compiled. C++ allows the use of pointers in the program, while Java restricts the use of pointers.

Why doesn’t Java make use of pointers?

Pointers are considered unsafe for beginner programmers, and Java is known for its code simplicity, so if pointers are used in that, it will make the program challenging. Also, pointer use is prone to errors, which often makes it hard to get utilized in Java.

Define instance and local variables.

Instance variables are the ones that are accessible by all the methods in a class. These variables are known for describing the properties of an object while remaining bound to it.

Local variable are those that are present within a block, function or function Object and variables be accessed within them. These variables function within the blocks only.

What are the default values assigned to the variables and instances in Java?

There are no values assigned to the variables in Java. Before using the variable, a proper initialization is done. For instances, a default value is initialized by the default function Object while creating an object. If it is a reference, it will be assigned the value null; if it is a numeric, it will take default value as 0; and if it initialized, it will be assigned the value False.

Define data encapsulation.

It is an object-oriented programming concept that hides the data attributes and their behaviors in a single unit. Developers find it useful to follow modularity while developing software. It is also used to secure the private properties of an object.

What is the difference between an interface and an abstract class?

An abstract class can be subclassed and contains both abstract and non-abstract methods that subclasses are forced to provide an implementation for, while an interface is completely an abstract class that is used to group the related methods with empty bodies.