Important Java interview questions and topics you need to know in 2022

Java interview questions

Java-related companies may not provide as much information about their interview format and process.

You may have narrowed down your list of potential employers based on recommendations from friends or colleagues.

Companies often include “Java interview questions” as a step in a job-application process. While some interviews can follow a straightforward,

the simple question-and-answer format, in the Java industry, preparing for an interview can be slightly more difficult.

One of the most challenging parts of the interview process is figuring out how to respond to interview questions.

And we are here to help you to figure out what kind of questions you have to face in your java interview for freshers and experienced professionals.

Having a list of topics or questions does not guarantee a good Java interview. However, if you know the content, it can put you ahead of many other candidates.

Important topics to consider for your Core java interview Questions

Basic and popular topics in Java
OOPS Concepts In Java

Object-oriented programming is essentially about allowing you to build a program using code that you’ve written before,

either exactly the same way or by applying changes. OOPS is frequently the typical approach of teaching anyone new to coding how to program.

Java Multithreading

Multithreading is the ability to execute more than one instruction at once, either within a single thread of control or in cooperation between several threads.

Serialization and Deserialization in Java

Serialization is a mechanism of converting the state of an object into a byte stream. Deserialization is the reverse process where the byte stream is used to recreate the actual Java object in memory.

Loops in Java

The Java for loop is used to iterate a part of the program several times. It is also called as a fixed loop since it iterates a specific number of times. We will see the syntax and some different types of loops in the next section.

Advanced Java Concepts:

Java Database Connectivity

Java Database Connectivity is an application programming interface for the programming language Java, which defines how a client may access a database. It is a Java-based data access technology used for connecting databases from within Java applications.


A servlet is a small Java program that runs within a Web server. Servlets receive and respond to requests from Web clients, usually across HTTP, the HyperText Transfer Protocol. To implement this interface, you can write a generic servlet that extends java. servlet.HTTP.<Servlet>, or extend an existing “base” servlet class.</Servlet>

JSP Java

Jakarta Server Pages is a collection of technologies that helps software developers create dynamically generated web pages based on HTML, XML, SOAP, or other document types. Released in 1999 by Sun Microsystems, JSP is similar to PHP and ASP but uses the Java programming language instead of scripting languages.

Java interview questions you need to know

What is defined as false sharing in the context of multithreading?

Reply: False sharing is known to be one of the familiar performance issues on multi-core systems, whereby each process has a local cache. This can potentially happen because parts of the data are stored at the same address in different pages of memory – a behavior that’s defined as false sharing. The actual amount of data that needs to be accessed for each call is usually very small, meaning that in total a large number of memory accesses is required. This can be hard to identify since the thread may be retrieving completely different global variables that occur to be fairly close together in memory.

How do you reverse a string in Java?

Reply: There is no reverse utility provided in Java. However, that does not mean we can’t reverse the string. In fact, what if you could form a character array from the string variable and iterate it from the end to the beginning? Wouldn’t that be amazing? I often ask this question when I chat with smart developers because it is important for them to be able to think out of the box.

Difference between Stack and Heap in Java

Reply: When programming in Java we have to worry about two different memory areas: Stack and Heap. In this Java tutorial, we will explain the difference between stack and heap in Java. The stack is usually much smaller than heap memory and also isn’t shared amongst multiple threads, but the heap is shared among all threads in JVM. In our journey on What is the difference between Stack and Heap in Java? You will learn how you can use Stack, when do you need to use it, why is it useful, etc.

What is the meaning of Enum type-safe in Java?

Reply: Java Enum defines a type-safe enumeration. What does this mean? In short, a type-safe Enum is an enumeration that knows its own type (it’s strongly typed) making it easier to use correctly. Unlike with classes, you cannot assign an instance of a different Enum type to an Enum variable and compile the code. This means that null pointer exceptions are impossible in an enum.

Difference between race conditions and deadlock in Java?

Reply: Error handling in a concurrent application can be difficult. A developer may think that they found the root cause of an issue, but there are still other threads sharing data with this code which they may not yet know exists. Deadlocks and Race Conditions occur frequently when developing a concurrent application using multiple threads. As a Java developer, it is important to know what the differences between the two are as well as how to troubleshoot and identify them in your application.

Explain a few methods of overloading best practices in Java?

Reply: Overloading a method in Java means that two or more methods have the same name, but accept different arguments.

In this blog post, I’m going to provide you with the best answer to overloading a method in Java to avoid confusion with auto-boxing.

Don’t overload method where one accepts ints and the other accepts Integer. Don’t overload method where a number of arguments are the same and only the order of argument is different.


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