U1) An Introduction To Core Java

Question 1

Who developed Java and when?

Answer 1

James Gosling in 1995 at Sun Microsystems.

Question 2

What was Java originally called?

Answer 2

Oak.

Question 3

What is the main feature of Java?

Answer 3

Write Once, Run Anywhere (WORA).

Question 4

List key features of Java.

Answer 4

Platform Independent, Object-Oriented, Simple, Secure, Robust, Multithreaded, Portable, High Performance, Distributed, Dynamic.

Question 5

How does Java ensure security?

Answer 5

Bytecode verification, Security Manager, sandboxing, and no direct memory access.

Question 6

How do you run a Java program using the command line?

Answer 6

Compile with ‘javac FileName.java’, run with ‘java FileName’.

Question 7

How do you create and run a Java program in an IDE?

Answer 7

Create new project, add class, write code, and run using IDE buttons.

Question 8

What are basic programming constructs in Java?

Answer 8

Decision-making (if, else, switch), looping (for, while, do-while).

Question 9

What is a class in Java?

Answer 9

A blueprint for creating objects.

Question 10

What is an object in Java?

Answer 10

An instance of a class.

Question 11

What is a constructor in Java?

Answer 11

A special method used to initialize objects.

Question 12

Define encapsulation.

Answer 12

Wrapping data and code into a single unit (class).

Question 13

Define abstraction.

Answer 13

Hiding internal details and showing functionality only.

Question 14

Define inheritance.

Answer 14

One class acquires the properties of another using ‘extends’.

Question 15

Define polymorphism.

Answer 15

The ability of one method to behave differently in different situations.

Question 16

How to use ‘super’ keyword?

Answer 16

To access parent class methods or constructor.

Question 17

How to use ‘this’ keyword?

Answer 17

Refers to the current class object.

Question 18

What does the ‘final’ keyword do?

Answer 18

Prevents method overriding or class inheritance.

Question 19

What is an interface in Java?

Answer 19

A reference type with abstract methods to be implemented by classes.

Question 20

How to implement an interface?

Answer 20

Use ‘implements’ keyword in the class definition.

Question 21

What is a package in Java?

Answer 21

A namespace that organizes a set of related classes and interfaces.

Question 22

How do you import a package?

Answer 22

Use ‘import packageName.ClassName;’ statement.

Question 23

What is exception handling?

Answer 23

Managing runtime errors using try-catch-finally blocks.

Question 24

What is the purpose of try-catch?

Answer 24

To catch and handle exceptions at runtime.

Question 25

What is the use of 'throw' and 'throws'?

Answer 25

'throw' is used to explicitly throw an exception; 'throws' declares exceptions in method signature.

Question 26

What is the use of 'finally' block?

Answer 26

Executes code regardless of whether an exception is thrown or caught.