Most Important Java Interview Questions


Students studying engineering or completing their studies from an engineering background will know the importance of programming knowledge. Especially if you want to get a job in a Top IT company, you have to know programming skills. This article will mention top java interview questions to enhance their skills because they can be the main factor for your selection. If you are from a Computer science or Information Technology background, it is the main key factor for finding any job in an IT company.

But not only for the students of this background but for anyone who wants to grow their career, especially in IT companies, they should at least have minimum knowledge of computers and programming. Among all programming languages, Java is a top programming language. In an interview, recruiters ask questions from Java. Some students find it difficult and don’t understand how questions can be asked. So in this article, we tried to mention top java interview questions which may ask in interviews.

January 27, 2022
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Table of Contents

Which are the most important java interview questions? 

Why is java so useful? 

If you are studying Java, you have to know this because it is a basic java interview question. Java is a top programming language. It’s a high-level object-oriented programming language used to develop games, device systems, and applications.

What is a class in Java interview questions? 

A collection of objects with common properties, relationships, and semantics is called class. A student object becomes a student class, and a collection of car objects becomes a car class.

What is static and dynamic loading? 

The generation of objects and instances using new keywords is required for static class loading. And when the name of the class is not known at compile-time, it’s called dynamic class loading.

What is the difference between JDK and JVM? 

It is considered a common Java interview question asked. At the same time, it is an important question also. We use JAVA Development Kit (JDK) for development purposes, and JAVA Virtual Machine(JVM) is a part of it. It executes the java programs. All the tools, executables, and binaries are there in JDK to compile a java program. And the execution part is handled by JVM.

What is the difference between JVM and JRE? 

Same for this also. Recruiters ask an important java interview question to check students’ knowledge. JAVA Runtime Environment (JRE) is the advanced version of JVM. For example, JRE consists of JVM, java binaries. And all other classes to execute any program. It doesn’t contain any tools like the Java compiler. To execute any java program, JRE should be installed.

What is the meaning of Double and Float variables in Java? 

In Java, Float takes 4 bytes in memory, and Double takes 8 bytes.

What is aggregation? 

You can create a weak relationship between two classes, where one class contains references to another class within it.

What is the “this” keyword in java? 

It is an important keyword used in Java. From within an instance method or a function Object, you can refer to any member of the current object by using “this”. In addition, you can use this to refer current class instance variable. And to invoke the current class constructor. It passed as an argument in the method call or any constructor call. It is also used to return the current class instance and invoke the current class method.

Java interview questions for freshers? 

What is data encapsulation and explain its significance? 

It is a concept of object-oriented programming for combining methods and properties in a single unit. It’s each object has its unique set of variables and methods. It also serves its functions independent of other subjects. You can also use Encapsulation for data hiding purposes.

What is the static keyword? 

IT is an important java interview question. We use it to make it global, and a class-level variable is also USD. So that all the objects will share the same variable, a static method can access only static variables.

What is an abstraction in JAVA? 

Objects are the building blocks of object-oriented programming. An object contains some properties and methods. Through access modifiers, we can hide them from the outer world. And we can provide access only for required functions and properties. This is the procedure to implement abstraction in OOPS.

In C/C++ we use pointers, but why in java we don’t use them? 

It’s an important java interview question. Recruiters ask it so many times in an interview. Java is a more simple language. The use of a pointer makes it more challenging. Sometimes it also causes potential errors in a code. Using pointers also compromises security because users can directly access the memory with the help of pointers. That’s why we don’t use pointers in Java. Moreover, it slows the procedure.

What are the features that make java one of the best programming languages? 

We know that Java is one of the top programming languages. Some features make Java one of the best programming languages. It’s a good question in terms of interviews. If you are a student who wants to work in IT companies, then you should have basic knowledge of Java. So it is a good java interview question to check your basic knowledge.

Simplicity: Java is simple than C/C++ languages. It is quite easy to learn and write.

OOPS– Java is based on the object-oriented programming system(OOPS). This means you can code in multiple objects with different data and behaviour.

Dynamic: Java is a complete dynamic language. It supports the loading of dynamic classes whenever required.

Platform independent– Java is also an independent platform, and it allows to run the programs to its platform only.

Security: No pointers are used in Java. And it also has the concepts of Bytecode exception handling, which makes Java a highly secure language.

What is the difference between an array and a vector in java? 

An array is the same group of data, and it is static. In comparison, Vectors are dynamic and hold different data types.

If lots of changes are required in data then which one we should use String or StringBuffer? 

We use StringBuffer when data is used too much. Because StringBuffer is dynamic, we can change its value too. But if we use String, then a String object will be created for every data change which is not wanted.

What is Multi-threading? 

Multi-threading is a programming concept that generates multiple tasks within a single program concurrently. Threads run in parallel. And it shares a stack of the same process. It enhances the performance of any program.

Java Interview questions for 5 years Experienced? 

What is a reflection and why is it useful? 

Reflection describes code that can inspect other code in the system to make modifications at runtime.

What is the function of CI (Continuous Integration)? 

CI function integrates all changes being made and committed by different developers. It also checks to compile errors. It builds code several times, especially after every commit to detect which commit made the breakage.

What is an inner class in java? 

We define a class inside a class, called nested classes. Inner classes are any non-static nested classes. Inner classes are linked to the class’s object and have access to all of the outer class’s variables and methods.

Difference between method overloading and overriding in java? 

Overriding happens at a subclass, but overloading happens in the same class. Overriding is a run time activity while overloading is resolved at compile time.

Why java is not completely object-oriented? 

It is an important java interview question, so you should read this before appearing for an interview. Java is not a completely object-oriented programming language, but it is still considered a pure programming language then compared to C, C++. It doesn’t support many object-oriented concepts like multiple inheritances, operator overloading, etc. Moreover, it still supports primitive datatypes like int, float, byte, double, short, etc., which are non-object. As a result, Java isn’t entirely an object-oriented programming language. It is an important java interview question and has been asked many times.

Software Engineering jobs

Students who study computer science or Information technology want to get a good job in an IT company. But many of you lack knowledge about software engineering jobs. Most of you may not know about the all job category and which one is suitable for you. This article also tried to mention some job categories that students choose as their careers.

Data Scientist- 

Suppose you are interested in working as a software engineer in any company. In that case, you can choose a data scientist as a career because it is related to a software engineering background. A data scientist is a professional responsible for collecting data and analyzing and interpreting extremely large amounts of data. Data Scientist role is an advanced role of several technical roles, mathematician and computer professionals.

Full-Stack Developer- 

Suppose you are a student from an engineering background and are interested in programming languages. Then you can become a full-stack developer. Its salary is also high and high in demand. Their main work is related to coding. They design and build websites according to their client’s demands with the help of HTML/CSS.

Software Developer- 

If you are interested in coding, you can also choose a career as a software developer. Its demand is high in top IT companies also. If you can learn some programming languages like C, C++, Java, Python, and Ruby, you can try. However, they want expert coders who specialize in all coding languages. Their work is to create innovative software programs and applications for customers’ needs.

Machine Learning Engineer- 

If any student is interested in starting their career as a machine learning engineer, it is a great choice. As nowadays its in demand and also salary package is high. If you are interested in machine learning and are an expert, this job is definitely for you.

If you want to work in a software engineering job, many choices are available. Like You can work as a Data Analyst or Blockchain Developer. Someone can work as an Information Systems Manager, Security Analyst, or Big Data Engineer.

About Chegg Question and Expert hiring 

Chegg is an online learning platform. They provide knowledge to students all over the world. Chegg helps students to improve their knowledge and to perform well in examinations. They help the students to learn in less time and low cost. Chegg provides solutions to different subjects. Like accounting, Engineering subjects, Math, Physics, Chemistry, Economy, Environmental Science, Geography, etc. One can choose any subject according to his preference.

Chegg hires subject matter experts as online teachers to provide quality solutions to the questions asked by the students. You need to clear the doubts of the students and give proper answers. Chegg will pay you for every correct answer. You can work as a freelancer through Chegg online platform.


So anyone interested to grow their career in software background or interested in computer knowledge then this article will help. Some students know, but they don’t have proper guidance on interview questions. Everyone knows the importance of an interview for selection. Especially if you want to apply for IT jobs, then in an interview, recruiters ask maximum questions from programming knowledge. So it is very important to know about all programming languages. One must know C, C++, Java, Python, and JavaScript. All languages are equally important depending on the role you are applying for.

Although many students find Java difficult because interviewers ask questions differently to confuse students, if you don’t know the pattern of asking questions in an interview, you may face trouble. That is why We tried to mention all possible java interview questions that anyone asks in an interview. It is for freshers and experienced also. Because question types may differ based on experience purpose.

In conclusion, I want to mention that reading all these questions before your interview will help you. You will feel more confident about the subject. And you will increase your chances of selection. Because of every small detail, we tried to mention it here. We also mention career options as a Software Engineer to guide students to chase their dream job.

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