Log InSign Up

17 Java Interview Questions (With Example Answers)

It's important to prepare for an interview in order to improve your chances of getting the job. Researching questions beforehand can help you give better answers during the interview. Most interviews will include questions about your personality, qualifications, experience and how well you would fit the job. In this article, we review examples of various java interview questions and sample answers to some of the most common questions.

Java Resume ExampleUse this template

or download as PDF

Common Java Interview Questions

What do you understand by the term Java?

There are a few reasons why an interviewer might ask this question:

1. To gauge the interviewee's level of expertise with Java. If the interviewee does not have a strong understanding of the term, the interviewer may question whether or not they are qualified for the position.

2. To see if the interviewee is familiar with the Java programming language. This is important because it shows whether or not the interviewee would be able to work with the company's existing codebase.

3. To determine if the interviewee is up-to-date with the latest trends in programming languages. Asking about Java shows that the interviewer is looking for someone who is knowledgeable about the latest technologies.

Example: “Java is a programming language and computing platform that enables developers to create robust, high-performance applications. Java is used in a wide variety of computing platforms from desktop computers to embedded devices.”

What are the features of Java?

One reason an interviewer might ask this question is to gauge the interviewee's level of expertise with the Java programming language. It is important to be able to discuss the features of Java in order to show that you have a strong understanding of the language. Additionally, this question can help to start a conversation about Java programming and best practices.

Example: “Java is a versatile and powerful programming language that enables developers to create robust, high-performance applications. Java is platform-independent, meaning that it can run on any operating system, and is widely used in a variety of industries. Some of the key features of Java include:

- Object-oriented: Java is based on an object-oriented model, which means that code is organized around objects rather than actions. This makes it easier to create modular, reusable code.

- Platform-independent: As mentioned above, Java can run on any operating system. This makes it an ideal choice for developing cross-platform applications.

- High performance: Java applications are compiled into bytecode, which can be executed by a Java Virtual Machine (JVM). Bytecode is highly optimized, making Java applications fast and efficient.

- Security: Java has built-in security features that prevent unauthorized access to sensitive data and resources.”

What is the difference between Java and other programming languages?

There are several reasons why an interviewer might ask this question. First, they may be trying to gauge the candidate's level of expertise with Java. Second, they may be trying to determine whether the candidate is familiar with other programming languages and, if so, how Java compares. Finally, the interviewer may be interested in the candidate's thoughts on the relative merits of Java versus other languages.

This question is important because it can help the interviewer to understand the candidate's level of expertise and also to get a sense for the candidate's thoughts on Java as a language.

Example: “Java is a high-level programming language that enables developers to create robust, high-performance applications. Java is platform-independent, meaning that programs written in Java can run on any operating system that supports the Java Runtime Environment (JRE). Other programming languages are specific to a particular platform and cannot be run on other platforms.”

What are the benefits of using Java?

There are many benefits of using Java, including its platform independence, its ease of use, its robustness, and its security.

Platform independence means that programs written in Java can run on any platform that supports Java without needing to be recompiled. This is possible because Java programs are compiled into bytecode, which can be run on any Java Virtual Machine (JVM).

Ease of use refers to Java's relatively simple syntax compared to other programming languages. This makes it easier to learn and less error-prone.

Robustness refers to Java's ability to handle errors gracefully. For example, if a program tries to access an array element that does not exist, Java will throw an exception instead of crashing the program.

Security is important because Java programs can be downloaded over the internet and executed on a user's computer. Java has built-in security features that prevent malicious code from doing damage.

Example: “There are many benefits of using Java, including:

1. Java is a versatile and powerful programming language that can be used for a wide variety of applications.

2. Java is platform-independent, meaning that it can be run on any operating system.

3. Java is open source and free to download.

4. Java has a large and active community of developers who contribute to the development of the language and its ecosystem of libraries and tools.

5. Java has well-defined standards and a consistent coding style, which makes it easy to read and maintain code written in Java.”

What do you understand by the term object-oriented programming?

There are a few reasons why an interviewer might ask a Java programmer what they understand by the term object-oriented programming. Firstly, it allows the interviewer to gauge the level of the candidate's understanding of the Java programming language. Secondly, it allows the interviewer to assess the candidate's ability to explain complex concepts in a clear and concise manner. Finally, it allows the interviewer to determine whether the candidate has a strong understanding of object-oriented programming principles and how they can be applied to real-world scenarios.

Example: “Object-oriented programming (OOP) is a programming paradigm that uses objects and their interactions to design and program applications. OOP focuses on data abstraction, encapsulation, modularity, and inheritance. These concepts were first introduced in the Simula programming language in 1967.”

What are the advantages of object-oriented programming?

There are many advantages of object-oriented programming, including the following:

1. Object-oriented programming is a powerful tool for modeling real-world objects and systems.

2. Object-oriented programming can help reduce the complexity of a program by breaking it down into smaller, more manageable pieces.

3. Object-oriented programming can make code more reusable and easier to maintain.

4. Object-oriented programming can make code more readable and understandable.

5. Object-oriented programming can help improve software quality by making it easier to catch and fix errors.

6. Object-oriented programming can make development faster and easier by providing a well-defined structure for code.

7. Object-oriented programming can allow developers to create programs that are more flexible and extensible.

8. Object-oriented programming can make it easier to develop graphical user interfaces (GUIs).

9. Object-oriented programming can make it easier to work with databases.

10. Object-oriented programming can help you learn other programming languages more easily.

Example: “There are many advantages to using object-oriented programming, including:

1. Increased flexibility: Objects can be created and used in a number of different ways, making code more flexible and adaptable.

2. Modularity: Code can be divided into small, self-contained modules (objects) that can be reused in other programs.

3. Extensibility: New functionality can be added to existing code by creating new objects.

4. Maintainability: Object-oriented code is generally easier to understand and maintain than other types of code.

5. Reusability: Objects can be reused in other programs, saving time and effort.”

What is the difference between object-oriented programming and procedural programming?

There are several reasons an interviewer might ask this question:

1. To gauge the candidate's familiarity with different programming paradigms. Object-oriented programming and procedural programming are two very different approaches to programming, and it is important for a programmer to be familiar with both.

2. To gauge the candidate's ability to think critically about different approaches to programming. By asking the candidate to compare and contrast these two approaches, the interviewer is assessing the candidate's ability to think critically about the strengths and weaknesses of each approach.

3. To gauge the candidate's ability to communicate clearly about technical topics. The candidate will need to be able to explain the difference between these two approaches in a clear and concise manner.

Example: “Object-oriented programming (OOP) is a programming paradigm that uses objects and their interactions to design and program applications. OOP focuses on data abstraction, encapsulation, modularity, and inheritance. These concepts are used to structure code in a way that makes it more understandable, reusable, and maintainable.

Procedural programming (PP) is a programming paradigm that follows a linear sequence of instructions to complete a task. PP is focused on writing code that is easy to follow and understand. This approach is typically used for small programs or programs that need to be completed quickly.”

What are the features of object-oriented programming?

There are several reasons why an interviewer might ask this question:

1. To assess whether the candidate is familiar with object-oriented programming concepts.

2. To gauge the candidate's ability to articulate complex technical concepts.

3. To see if the candidate can provide concrete examples of how object-oriented programming can be used to solve real-world problems.

4. To determine whether the candidate has a strong understanding of Java's object-oriented features.

5. To find out if the candidate is able to apply object-oriented programming concepts to real-world scenarios.

6. Finally, this question allows the interviewer to get a sense for the candidate's overall coding abilities.

Example: “1. Object-oriented programming is a programming paradigm that is based on the concept of objects.
2. These objects are composed of data and methods that operate on that data.
3. Objects can be created from templates called classes.
4. Once an object is created, it can be used like any other variable in the program.
5. Objects can be passed as parameters to methods and they can be returned from methods.
6. Objects can also inherit behavior from other objects (known as inheritance).”

What do you understand by inheritance in Java?

Inheritance is an important concept in Java because it allows programmers to create relationships between classes and to reuse code. By understanding inheritance, programmers can more easily create and maintain complex Java applications.

Example: “Inheritance is one of the key features of object-oriented programming in Java. It allows a child class to inherit the properties and methods of its parent class. This means that the child class can access all the members of the parent class, including private members. Inheritance also allows the child class to override methods of the parent class, if necessary.”

What are the different types of inheritance in Java?

There are four types of inheritance in Java: single, multilevel, hierarchical, and hybrid.

It is important to know the different types of inheritance in Java because they determine how classes can be related to each other, and how subclass objects can be created and used.

Example: “There are three types of inheritance in Java:

1. Single Inheritance: A class inherits from another single class.

2. Multiple Inheritance: A class inherits from multiple classes.

3. Multilevel Inheritance: A class inherits from another class, which in turn inherits from another class.”

What is multiple inheritance?

There are a few reasons an interviewer might ask a question about multiple inheritance:

1. To gauge the candidate's understanding of Java's inheritance model. In Java, multiple inheritance is not possible, so it is important for the candidate to know this.

2. To see if the candidate is familiar with other languages that do support multiple inheritance. This can be important in some cases, as it can help the interviewer understand how the candidate thinks about and approaches problems.

3. To better understand the candidate's thought process and how they approach solving problems. This question can help the interviewer understand how the candidate breaks down and thinks about complex topics.

Example: “Multiple inheritance is a feature of some object-oriented programming languages in which an object or class can inherit characteristics and behavior from more than one parent object or parent class.”

What are the advantages and disadvantages of multiple inheritance?

Multiple inheritance is a feature of some object-oriented programming languages in which an object or class can inherit characteristics and behavior from more than one parent object or class.

The advantages of multiple inheritance are that it can represent complex relationships between objects more accurately than single inheritance, and that it can allow for more code reuse. The disadvantages of multiple inheritance are that it can make code more difficult to understand and maintain, and that it can lead to the "diamond problem" (explained below).

The diamond problem is a potential issue that can arise when using multiple inheritance. The problem occurs when two classes inherit from a common superclass, and then a third class inherits from both of those classes. This can lead to ambiguity about which version of a particular method or attribute should be used.

Example: “There are both advantages and disadvantages to using multiple inheritance. Some of the advantages include the ability to model complex relationships more accurately, and the ability to reuse code more efficiently. However, some of the disadvantages include the potential for increased complexity in code, and the potential for ambiguity when multiple inherited classes have conflicting methods or data members.”

What do you understand by polymorphism in Java?

Polymorphism is the ability of an object to take on many different forms. The most common use of polymorphism in Java is through inheritance, when a subclass can take on the behavior of its superclass. Polymorphism is important because it allows for code reuse and flexibility.

Example: “Polymorphism is the ability of an object to take on different forms. In Java, polymorphism refers to the ability of a class to take on multiple forms. A class can take on multiple forms by implementing multiple interfaces. A class can also take on multiple forms by extending multiple classes.”

What are the different types of polymorphism in Java?

There are four types of polymorphism in Java: method overriding, method overloading, coercion, and interfaces.

Method overriding is when a child class defines a method that already exists in the parent class. The child class is said to be overriding the parent class's method. This is important because it allows for different behavior in the child class, while still maintaining the same interface in the parent class.

Method overloading is when multiple methods in a class have the same name but different signatures. This is important because it allows for different behavior depending on the input to the method.

Coercion is when a value of one type is automatically converted to another type. This is important because it allows for values to be used in places where they normally wouldn't be able to be used.

Interfaces are like contracts that specify what a class must do. This is important because it allows for classes to be written that conform to a specific interface, which makes code more reusable and easier to understand.

Example: “Polymorphism in Java can be broadly classified into two types: compile-time polymorphism and runtime polymorphism.

Compile-time polymorphism is also known as static binding or early binding. It is a type of polymorphism in which the type of object is determined at compile time. In other words, the decision of which method to call is made during compilation of the program, based on the static (i.e. compile time) type of the object. For example, consider the following code:

public class Test {
public static void main(String[] args) {
A a = new A();
B b = new B();
a.display(); // calls display() method of class A
b.display(); // calls display() method of class B
}
}
class A {
public void display() {
System.out.println("Inside A's display method");
}
}
class B extends A {
public void display() { // overriding method
System.out.println("Inside B's display method");
}”

What is method overloading in Java?

Method overloading is a feature that allows a class to have more than one method with the same name, but with different parameters. This is important because it allows for more flexibility and functionality when creating methods. For example, a class might have a method that takes an integer and another method that takes a string. By overloading the methods, the class can handle both types of input.

Example: “Method overloading is a feature in Java that allows a class to have more than one method with the same name, but with different parameters. This is useful when you want to provide different functionality depending on the type or number of arguments passed to the method. For example, you could have a method that accepts an int and returns an int, and another method that accepts a double and returns a double.”

What is method overriding in Java?

One reason an interviewer might ask "What is method overriding in Java?" is to gauge the interviewee's understanding of the Java programming language. In particular, method overriding is a key concept in object-oriented programming, and it is important for Java developers to understand how it works. Additionally, method overriding can be used to improve the performance of Java programs, so it is important for interviewees to be familiar with its use.

Example: “Method overriding is a feature that allows a child class to provide a specific implementation of a method that is already defined in the parent class. The child class can override the method by providing its own definition of the method with the same name, same parameters, and same return type as the method in the parent class.”

What are the differences between method overloading and method overriding in Java?

There are several reasons an interviewer might ask this question:

1. To gauge the candidate's understanding of basic Java concepts.

2. To see if the candidate can explain the differences between two similar concepts in a clear and concise manner.

3. To determine if the candidate is familiar with common Java programming patterns.

4. To assess the candidate's ability to think critically about code.

5. To gauge the candidate's ability to communicate effectively with others about code.

Overall, this question is important because it tests a number of different skills and knowledge areas that are important for any Java programmer.

Example: “Method overloading is a feature that allows a class to have more than one method with the same name, but with different parameters. This is useful when you want to provide different functionality depending on the type or number of arguments.

Method overriding is a feature that allows a subclass to override a method defined in its superclass. This is useful when you want to change the behavior of a method inherited from a superclass.”

Related Interview Questions