JAVA Interview Questions and Answers in 2025 (100+ Q&A)

Ques:- How can I connect from an applet to a database on the server?

Asked In :- MSys Technologies, valuebound,

Right Answer:
To connect from an applet to a database on the server, you should use a server-side technology like Java Servlets or JSP to handle the database connection. The applet can make HTTP requests to the server, which will then interact with the database and return the results to the applet. Direct database connections from applets are not recommended due to security restrictions.

JAVA Team Lead/ Tech Lead

Ques:- What is servlet ,what is the use of it?

Asked In :- navvis,

JAVA System Security Engineer

Ques:- What is the difference between a Driver and a DataSource (in Java JDBC)?

Asked In :-

Right Answer:
A Driver is a specific implementation that allows Java applications to connect to a database, while a DataSource is a higher-level interface that provides a way to obtain connections to a database and can also support connection pooling and distributed transactions.

JAVA System Security Engineer

Ques:- What is meant by polymorphism in java?How can we achieve polymorphism?Explain with an example.

Asked In :- qnx software systems, samsung r&d institute bangladesh,

Right Answer:
Polymorphism in Java refers to the ability of a single interface to represent different underlying forms (data types). It allows methods to do different things based on the object that it is acting upon.

We can achieve polymorphism in Java through:

1. **Method Overloading** (Compile-time polymorphism): Multiple methods with the same name but different parameters.
2. **Method Overriding** (Runtime polymorphism): A subclass provides a specific implementation of a method that is already defined in its superclass.

**Example:**

```java
class Animal {
void sound() {
System.out.println("Animal makes a sound");
}
}

class Dog extends Animal {
void sound() {
System.out.println("Dog barks");
}
}

class Cat extends Animal {
void sound() {
System.out.println("Cat meows");
}
}

public class TestPolymorphism {
public static void main(String[] args) {
Animal myDog = new Dog();
Animal

JAVA Team Lead/ Tech Lead

Ques:- How are the implicit object made available in the jsp file? Where are they defined?

Asked In :- D H, PRORIGO SOFTWARE PVT, Wexford County Council, Mitsogo Technologies, wolt, jouve,

JAVA Team Lead/ Tech Lead

Ques:- What is Log4j in java

Asked In :- Synture, GO Outdoors, Atypon Systems, rapyuta robotics,

JAVA Team Lead/ Tech Lead

Ques:- How do I implement a RowSetReader? I want to populate a CachedRowSet myself and the documents specify that a RowSetReader should be used. The single method accepts a RowSetInternal caller and returns void. What can I do in the readData method?

Asked In :- gmt, lightyear.one,

JAVA Team Lead/ Tech Lead

Ques:- What is the difference between array list and linked list. in which situations we are use them? which is best one?

Asked In :-

JAVA Team Lead/ Tech Lead

Ques:- What is cohesion and coupling in java?

Asked In :- Finoit Technologies, vacasa,

JAVA Team Lead/ Tech Lead

Ques:- How can I secure the communication between SAP JCo and an SAP System?

Asked In :- Forsys, thunderhead,

JAVA System Security Engineer

Ques:- What is the first statement in construtor?

Asked In :- BlueRose Technologies, nintex, prescient technologies,

Right Answer:
The first statement in a constructor must be either a call to another constructor in the same class (using `this()`) or a call to a superclass constructor (using `super()`).

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Ques:- Is there a way to reference the “this” variable within a JSP page?

Asked In :- Tecnotree, Sonora Software, starmark software,

JAVA Team Lead/ Tech Lead

Ques:- Solve it… public class test {public static void main(String[] args) {int i=5;i=i++;System.out.println(“result::”+i);}}

Asked In :- MSys Technologies, bloomreach, progneur,

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Ques:- What's the JDBC 3.0 API?

Asked In :- coditas,

JAVA Team Lead/ Tech Lead

Ques:- What are the considerations for deciding on transaction boundaries?

Asked In :- Artech Infosystems, mitratech, sbl, catalyte,

JAVA Team Lead/ Tech Lead

Ques:- When I intersperse table creation or other DDL statements with DML statements, I have a problem with a transaction being commited before I want it to be. Everything ( commit and rollback ) works fine as long as I don't create another table. How can I resolve the issue?

Asked In :- sbl, incorta,

JAVA Team Lead/ Tech Lead

Ques:- What is the SAP Java IDoc Class Library?

Asked In :- sbl,

JAVA System Security Engineer

Ques:- Why clonning method is private?can u overload the main() method.2)can overload the run() method.3)what is Common Separated value.

Asked In :- zemoso technologies, iopex technologies, samsung r&d institute bangladesh,

Right Answer:
1) The `clone()` method is private to prevent unauthorized access and modification of the object's state, ensuring that cloning is controlled and consistent.

2) Yes, you can overload the `main()` method by defining multiple versions with different parameter lists.

3) Common Separated Values (CSV) is a file format that uses commas to separate values, allowing data to be stored in a tabular format, typically used for importing and exporting data between applications.

JAVA System Security Engineer

Ques:- Can you tell me the steps for how to create and execute and run the Ejb simple stateless session application in websphere application server6.0 and Ide is RAD6.0

Asked In :- Cateina Technologies, psiog digital, vortex global services,

Right Answer:
1. **Set Up Environment**: Ensure WebSphere Application Server 6.0 and RAD 6.0 are installed and configured.

2. **Create a New EJB Project**:
- Open RAD 6.0.
- Go to File > New > Project.
- Select "EJB Project" and click Next.
- Enter the project name and configure the settings as needed.

3. **Create Stateless Session Bean**:
- Right-click on the EJB project > New > Session Bean.
- Choose "Stateless" and provide the bean name and interface details.
- Implement the business logic in the bean class.

4. **Configure Deployment Descriptor**:
- Open `ejb-jar.xml` and configure the bean settings if necessary.

5. **Create a Client Application**:
- Create a new Java project or a Java class within the EJB project to act as a client.
- Use JNDI to look up the

JAVA Team Lead/ Tech Lead

Ques:- What is the difference between bean:write and bean:message

Asked In :- CriticalRiver, brain station 23 limited,

The Java skill section on takluu.com is designed for freshers, intermediate developers, and experienced professionals aiming to crack Java-based technical interviews with confidence. Java remains one of the most in-demand programming languages, and mastering it opens the door to countless opportunities in backend development, enterprise solutions, Android apps, and cloud-based platforms.

Our Java category covers everything from Core Java concepts like OOPs (Object-Oriented Programming), Data Types, Loops, and Exception Handling to Advanced Java topics including Collections Framework, Multithreading, JDBC, Servlets, JSP, Lambda Expressions, and Streams. We provide practical coding examples, real interview questions (with answers), and key concept explanations that interviewers commonly test.

Whether you’re applying for a role like Java Developer, Backend Engineer, or Full Stack Developer, this section ensures you understand the logic, syntax, and problem-solving approaches that matter in real-world interviews. You’ll also find scenario-based questions and discussions around design patterns, JVM internals, garbage collection, and performance tuning — areas often explored in senior-level interviews.

Each topic is structured to help you revise quickly and efficiently, with quizzes and mock interviews to assess your understanding. Our content is curated by experts who have worked with Java across different domains and keep the material aligned with current industry trends.

At Takluu, we believe in not just learning Java — but preparing to think in Java. Get ready to face interviews with clarity, confidence, and a deep understanding of what makes Java so powerful and reliable.

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