Java J2ee Developer

10+ Java J2ee Developer Interview Questions and Answers

Updated 2 Jul 2025
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Asked in DXFactor

3d ago

Q. How would you call multiple APIs and fetch data from each API sequentially?

Ans.

To call multiple APIs and fetch data sequentially, use asynchronous calls and handle responses in order.

  • Use asynchronous calls to make API requests in parallel

  • Handle responses in order to ensure data is fetched sequentially

  • Use promises or callbacks to manage the flow of data retrieval

Asked in DXFactor

4d ago

Q. What are the operations for adding and removing elements in an ArrayList in Java?

Ans.

Operations for adding and removing elements in an ArrayList in Java

  • To add an element to an ArrayList, use the add() method with the index where you want to insert the element

  • To remove an element from an ArrayList, use the remove() method with the index of the element you want to remove

  • Example: ArrayList<String> list = new ArrayList<>(); list.add("Apple"); list.add("Banana"); list.remove(0); // Removes Apple

Asked in DXFactor

6d ago

Q. What is an example of session start and end in programming?

Ans.

Session start and end in programming refers to the beginning and termination of a user's session on a website or application.

  • Session start occurs when a user logs in or visits a website, creating a unique session ID.

  • Session end happens when the user logs out or closes the browser, terminating the session.

  • Example: In Java servlets, HttpSession object is used to manage session start and end.

Asked in DXFactor

4d ago

Q. What is the process to synchronize an ArrayList in Java?

Ans.

Use synchronizedList() method to synchronize an ArrayList in Java.

  • Create a synchronized list using Collections.synchronizedList() method.

  • Example: List<String> synchronizedList = Collections.synchronizedList(new ArrayList<>());

  • Access and modify the synchronized list using synchronized blocks to ensure thread safety.

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Asked in Baker Hughes

4d ago

Q. What is the difference between an abstract class and an interface in Java?

Ans.

Abstract classes and interfaces are both used to achieve abstraction in Java, but they have distinct features and use cases.

  • Abstract Class: Can have both abstract methods (without implementation) and concrete methods (with implementation). Example: 'abstract void draw();' and 'void fill() { ... }'.

  • Interface: Can only have abstract methods (prior to Java 8) and default/static methods (from Java 8 onwards). Example: 'void draw();' and 'default void fill() { ... }'.

  • Multiple Inhe...read more

Q. What is a JDBC driver, and what are the different types of drivers?

Ans.

JDBC driver is a software component that enables Java applications to interact with databases.

  • JDBC driver acts as a mediator between Java application and database.

  • There are four types of JDBC drivers: Type 1, Type 2, Type 3, and Type 4.

  • Type 1 driver uses ODBC to connect to the database.

  • Type 2 driver uses native API to connect to the database.

  • Type 3 driver uses a middle-tier server to connect to the database.

  • Type 4 driver is a pure Java driver that connects directly to the dat...read more

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Asked in DXFactor

3d ago

Q. What is a synchronous call in JavaScript?

Ans.

A synchronous call in JavaScript is a function call that blocks the execution of the code until it completes.

  • Synchronous calls wait for the function to finish before moving on to the next line of code.

  • They can cause the program to become unresponsive if the function takes a long time to complete.

  • Example: Using the 'fetch' API to make a synchronous call to a server.

Asked in DXFactor

1d ago

Q. What is the default value of an ArrayList in Java?

Ans.

The default value of an ArrayList in Java is an empty ArrayList.

  • Default value is an empty ArrayList, which means it has a size of 0.

  • The ArrayList will not have any elements stored in it by default.

  • Example: ArrayList<String> list = new ArrayList<>(); // Default value is an empty list.

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Asked in Azimuth GRC

2d ago

Q. What is multithreading, and how is it implemented in Java?

Ans.

Multithreading is a Java feature that allows concurrent execution of two or more threads for improved performance.

  • Java supports multithreading through the Thread class and the Runnable interface.

  • To create a thread, extend the Thread class or implement the Runnable interface.

  • Example of extending Thread: class MyThread extends Thread { public void run() { // code } }

  • Example of implementing Runnable: class MyRunnable implements Runnable { public void run() { // code } }

  • Threads c...read more

Asked in Synechron

6d ago

Q. What is a concurrent HashMap?

Ans.

ConcurrentHashMap is a thread-safe version of HashMap in Java.

  • ConcurrentHashMap allows multiple threads to read and write to the map concurrently without the need for external synchronization.

  • It achieves this by dividing the map into segments, each of which can be locked independently for better performance.

  • ConcurrentHashMap is part of the java.util.concurrent package and was introduced in Java 5.

  • Example: ConcurrentHashMap<String, Integer> map = new ConcurrentHashMap<>();

Asked in Infosys

1d ago

Q. Explain the OOPS concepts.

Ans.

OOPS concepts are the principles of Object-Oriented Programming that help in designing and implementing software systems.

  • Abstraction: Hiding implementation details and showing only necessary information.

  • Encapsulation: Binding data and methods together to protect data from outside interference.

  • Inheritance: Creating new classes from existing ones to reuse code and add new features.

  • Polymorphism: Using a single interface to represent multiple entities.

  • Objects: Instances of classe...read more

Q. Explain the servlet lifecycle.

Ans.

Servlet lifecycle involves initialization, service, and destruction phases.

  • Servlet is initialized by calling init() method

  • Service method is called for each request

  • Servlet is destroyed by calling destroy() method

  • Container manages the lifecycle of servlet

  • ServletConfig and ServletContext objects are available during initialization

Asked in TCS

2d ago

Q. Explain the Java Collection Framework.

Ans.

Collection is a framework that provides an architecture to store and manipulate a group of objects.

  • Collection is an interface in Java that extends Iterable interface.

  • It is used to store a group of objects.

  • Collections can be of two types: List and Set.

  • List is an ordered collection that allows duplicates while Set is an unordered collection that does not allow duplicates.

  • Examples of collections include ArrayList, LinkedList, HashSet, TreeSet, etc.

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