Java Coding Interview Questions For 3 Years Experience


Java Coding Interview Questions For 3 Years Experience


Java is one of the most widely used programming languages, and having 3 years of experience in it is a significant achievement. During a coding interview for a 3 years experienced Java developer, the interviewer may ask questions to assess your knowledge and skills in various areas such as core concepts of Java, object-oriented programming, data structures, algorithms, multithreading, and exception handling.


Some common java coding interview questions for 3 years experienced candidates may include implementing various data structures like arrays, linked lists, stacks, and queues, understanding concepts like inheritance, polymorphism, and abstraction, solving coding problems using algorithms like sorting and searching, designing solutions for real-world problems, and handling exceptions effectively.


The interviewer might also ask about your experience with Java libraries and frameworks like Spring, Hibernate, or JavaFX and your understanding of design patterns like Singleton, Factory, or Observer. Other questions may revolve around your experience with database integration, web development using Java, and skills in debugging and optimizing code.


To excel in a coding interview for a 3 years experienced Java developer, you should be well-versed in the fundamentals of Java, have a strong understanding of object-oriented programming principles, and be able to write efficient, clean, and maintainable code. It is also essential to have hands-on experience with various tools and technologies related to Java development and to demonstrate knowledge of industry best practices and coding standards.

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 1 - Why do you think you are qualified for this job?


  I have three years of experience working as a Java developer, which has allowed me to gain a deep understanding of the language and its various components. During this time, I have worked on a diverse range of projects, from web applications to mobile applications, which have given me a well-rounded understanding of Java's capabilities. I have also actively sought out opportunities to improve my skills, such as attending conferences and workshops, and I am always eager to learn new technologies and techniques to improve my development abilities.

2) Can you explain the difference between an abstract class and an interface in Java?

An abstract class is a class that cannot be instantiated but can have both abstract and concrete methods, whereas an interface is a blueprint of a class that can only contain abstract methods. An abstract class can also have non-static and non-final variables, while an interface can only have static and final variables. Additionally, a class can only extend one abstract class, but it can implement multiple interfaces.

3) What is the importance of the keyword “static” in Java?

The keyword “static” is used to declare a variable or a method as belonging to the class rather than an instance of the class. This means that the variable or method can be accessed without creating an object of the class. It is commonly used for defining constants and utility methods in Java.

4) How do you handle exceptions in Java?

In Java, exceptions can be handled using a try-catch block. The code that can potentially throw an exception is enclosed in the try block, and the corresponding catch block is used to handle the exception. Additionally, we can also use a finally block to perform any necessary clean-up operations, regardless of whether an exception occurs or not.

5) Can you explain the difference between a HashMap and a HashTable in Java?

Both HashMap and HashTable are used for storing key-value pairs in Java. However, HashMap is not thread-safe and allows for the insertion of null values, while HashTable is thread-safe and does not allow null values. HashTable also uses synchronized methods, which can impact performance, while HashMap uses non-synchronized methods.

6) What is the purpose of the “finalize” method in Java?

The “finalize” method in Java is used for performing any necessary clean-up operations before an object is garbage collected. It is called just before the object is destroyed and can be used to release any resources, such as file handles, that the object may be holding.

7) How do you enable garbage collection in Java?

Garbage collection in Java is automatically enabled by the JVM. However, we can manually trigger garbage collection using the “System.gc()” method, although it is not recommended as it may impact performance.

8) Can you explain the difference between a “StringBuilder” and a “StringBuffer” in Java?

Both StringBuilder and StringBuffer are used for creating mutable strings in Java. However, StringBuffer is thread-safe and slower compared to StringBuilder, which is not thread-safe but has better performance.

9) How do you convert a String to an int in Java?

To convert a String to an int in Java, we can use the “Integer.parseInt()” method. This method takes a String as an input and returns an int value.

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10) What is the difference between a “Class” and an “Object” in Java?

A Class is a blueprint or template for creating objects, while an Object is an instance of a Class. A Class can contain attributes and methods, which define the characteristics and behavior of the objects that are created from it.

11) What is the use of the “this” keyword in Java?

The “this” keyword refers to the current instance of the class and can be used to differentiate between class variables and parameters with the same name. It can also be used to call another constructor within the same class.

12) Explain the concept of inheritance in Java.

Inheritance is a fundamental principle of object-oriented programming, where a child class can inherit properties and methods from a parent class. This allows for code reusability and helps to avoid redundant code.

13) How do you create and run a thread in Java?

A thread can be created in Java by extending the “Thread” class or implementing the “Runnable” interface and overriding the “run()” method. The thread can then be started using the “start()” method. To run a thread, we can use the “join()” method to wait for the thread to finish execution.

14) What is the difference between a “static” and a “non-static” method in Java?

A static method belongs to the class and can be accessed without creating an object of the class, while a non-static method belongs to the object and can only be accessed through an object of the class.

15) How do you handle concurrent access to resources in Java?

In Java, we can handle concurrent access to resources using synchronization. This can be achieved by using the “synchronized” keyword or by using the “Lock” interface and its implementations. This ensures that only one thread can access a particular resource at a time, preventing concurrency issues.


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