Top 20 Java Questions To Crack An Interview In 2020

How important is a programming language?

If you are not a caveman, you probably know the answer to this.

There is no trending technology with which you can pursue a career without knowing a thing about programming languages. Isn’t it? And if you are a developer, you already know that there is not a single day in your profession that passes by without programming languages.

So, which programming language you should emphasize on? Which is the one language that is universally used by most of the organizations? 

Of course, it’s Java!

Java has been around for quite some time but still hasn’t lost its charm even a bit. Java is basically Object-oriented programming (OOP), a  programming paradigm that is based on the concept of objects that contain data, in the form of attributes or properties. OOP languages are diverse, but the most popular ones are class-based, where the objects are instances of classes, determining their price.

Being an object-oriented programming language, organizations are broadly using Java with top trending technologies to reach the peak of success.

Hence, irrespective of the career path you choose, you can expect the following 20 Java interview questions coming on your way. Check them out once!

 

1. Define Class in Java.

A class in Java is basically a template used to create objects and define the data type. It mainly acts as a building block for Java language-oriented systems.

2. What is the difference between Static and Dynamic Loading?

Static class loading creates objects and instances with the help of new keywords. On the other hand, dynamic class loading works in that particular time when the name of the class is not known at compile time.

3. What Is Multi-Threading?

Multi-threading is a programming concept that is used to run multiple tasks in a happening way within one single program.

4. When and by Whom was Java Developed?

James Gosling developed Java in Sun Microsystem in the year of 1995.

5. What Do JDK, JRE, and JVM Stand for?

JDK, JRE, and JVM stand for:

• JVM- Java Virtual Machine
• JRE- Java Runtime Environment
• JDK- Java Development Kit

6. Does Java Use Pointers?

Java doesn’t use pointers since it has tough security. Java uses references instead of pointers as they are much safe and more secure compared to a pointer.

7. How Do You Connect to a Database in Java?

To connect to a database in Java  you need to follow these following steps:

• Register to the driver class
• Create connection
• Create statement
• Execute queries
• Close connection

8. What Are the Functions of JVM and JRE?

JVM provides a runtime environment through which Java Byte Codes can be executed. 

JRE stores the sets of files required by JVM during runtime.

9. What Is the Difference Between Overloading and Overriding?

When two methods have the same name but different properties, it is overloading. On the other hand,  Overriding happens when two methods have the same name and same properties, one belongs to the child class and the other belongs to the parent class.

10. What Is the Default Size of the Load Factor in Hashing a Based Collection?

The default size of a load factor is 0.75, and the default capacity can be computed as:

  Initial capacity * Load factor 

11. What Is a Package?

A package is a collection of related classes and interfaces in Java.

12. What's the Base Class of all Exception Classes?

 Java.lang.Throwable is the superclass of all exception classes that are derived from this base class.

13. What Is the Difference Between equals() and = =?

 Equals() method helps in checking the equality of two objects that are defined by business logic.

 == is known as an equality operator that is used to compare primitives and objects.

14. State Two Differences Between an Inner Class and a Subclass.

Although Inner classes reside in the same file, subclasses can be placed in another file. Also,  subclasses work with the methods of their parent class whereas inner classes can work with the methods they want.

15. How Are Destructors Defined in Java?

Java has its own garbage collection. Hence, no destructors are required to be defined.   Destruction of the objects is automatically carried by the garbage collection mechanism.

16. Define JSON.

JSON is an acronym for JavaScript Object Notation. It uses JavaScript syntax in a text-driven format.

17. Name the Most Important Feature of Java.

Java is a platform-independent language.

18. What Is an Anonymous Class?

Anonymous Class is a class that is defined without any name in a single line of code using a new keyword.

19. What Is a JVM?

JVM stands for Java Virtual Machine. It is a runtime environment for compiled Java class files.

20. Can a Dead Thread Be Started Again?

 No, a thread that is in the dead state can't be started again.

Conclusion:

Don’t you think they are pretty simple to learn? You have already learned all of it during your graduation. Now, all you need to do is refresh your Java memories a little bit. Isn’t it?

So let’s focus on that. And once you are completely prepared, don’t forget to have a look at our vast range of training courses and pick what you think is best for you!

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