Top Java Interview Questions with Answers for 2021

A perennial contributor to the software development domain for several years, Java has proved to be one of the most widely used programming languages. In this article, we will talk about the top java interview questions. It is necessary to know about the top java programming skills and to also practice these skills. These java interview questions will help you ace the interview and get your dream job. These java interview questions can be helpful for experienced professionals and for freshers as well. Let us take a look at some of the top questions.

Java Interview Questions and Answers 2021

1. What is Java?

A general-purpose programming language, Java is class-based and object-oriented. It is one of the most popular programming languages in the world. Let us look at a small example of a program in Java. 

Hello World Example-

public class FileName {

public static void main(String args[]) {

System.out.println(“Hello World!”);

}

}

2. What do you mean by enumeration in Java?

A list of named constants is known as enumeration. It is used to define a class type in java, and can have methods, constructors, and instance variables as well. To create enumeration in Java, you should use the enum keyword. By default, all enumerations in java are public, final, and static. Although the enumeration defines a class type and has constructors, we don’t need to instantiate an enum by using new. These variables are declared the same way as a primitive variable. 

3. What do you mean by encapsulation in Java?

If you want to hide the implementation details from the users, you can use encapsulation. Let’s say that a data member is private, this means that it can be accessed only within one class and no outside variables or private data members of other classes. However, if a public getter and setter method is set up to read [example String getName()] and update [example void setName(String Name)], then, these private data fields can be accessed via public methods. 

4. What do you understand by collection in Java?

Containers who can group multiple items in a single unit are known as collections. A list of names, or a jar of biscuits are two examples of a container. In every programming language, such collections are used. When Java was introduced, it came with a number of collection classes such as Hashtable, Array, Stack, and Vector. 

5. Explain the term API in Java. 

API or Java application programming interface is a list of all the classes that comprise the java development kit or JDK. Java classes, packages, interfaces, along with their fields, methods, and constructors are included within an API. Since these classes are pre-written, it gives the programmer a great amount of flexibility and functionality. 

6. What do you mean by Static in Java?

If a member of a class is not associated with an instance of a class, this is known as a static member in java. A static member belongs to the class itself, and as a result, it is possible to access a static member in Java without having to create a class instance.

7. What is a package in Java?

In Java, a package is used to group classes that are related. We can think of a package as a folder within a file directory. Packages are mainly used to avoid name conflicts, and to write code that is better maintainable. The packages in java can be divided mainly into two categories, namely, Built-in Packages, and User-defined Packages.

8. How can you enable Java in chrome?

  • Go to the Java Control Panel
  • Click Security Tab
  • Click on Apply & click OK to confirm changes
  • Restart the browser to enable the changes

9. What do you mean by string in Java?

A sequence of characters is known as a string. For example, “programming” is a string of 11 characters. A string is an immutable object and cannot be changed after it has been created. 

10. What is multiple inheritance not supported by Java?

Multiple inheritance is supported by java through interfaces only. Any number of interfaces can be implemented in a class, but it can extend only one class. The reason for not supporting multiple inheritance is that it creates a diamond problem. 

11. Explain singleton class in java? 

If you want to restrict the instantiation of a class and ensure that this class exists only in JVM, you should use the singleton design pattern. A class that can have one object, or one instance of the class at a time per JVM, is known as a singleton class in java. 

12. What do you mean by garbage collection in java?

An automatic process in which the programmer need not explicitly mark the objects that need to be deleted is known as garbage collection in java. You can implement this in JVM and the JVM implements the garbage collection however it pleases. However, there is one requirement, and this is to meet the JVMs specifications. The most common JVM is Oracle’s HotSpot as it offers a robust set of options for garbage collection in java.

Conclusion

This brings us to the end of the blog on java interview questions and answers. We hope that you found this blog helpful and were able to refresh your memory regarding the basic concepts in java and learn something new as well. These top java interview questions are helpful for freshers as well as experienced professionals. We wish you all the best in your future endeavors and hope that you are able to ace your java interview process. 

Frank Meyer

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