JNTU B.Tech II JAVA PROGRAMMING Previous Question Paper (August/September - 2022 - R13)

Data Abstraction is the process of hiding implementation details and showing only the essential features of an object. In Java, this is achieved using abstract classes and interfaces. For example, a Shape abstract class defines a method draw(), while specific subclasses like Circle or Rectangle provide the actual implementation.

Encapsulation is the mechanism of wrapping data (variables) and code (methods) together as a single unit. It is achieved by declaring class variables as private and providing public getter and setter methods to access them, ensuring data security. For example, a Student class with a private rollNumber field accessed via getRollNumber().

Inheritance is a mechanism where a new class acquires the properties and behaviors of an existing class. It promotes code reusability. For example, a Manager class can extend an Employee class to inherit common attributes like name and id, while adding specific attributes like department.

Java defines two main categories of data types: Primitive and Non-Primitive.

Primitive Data Types are predefined by the language and hold single values:

• byte: 8-bit signed integer.
• short: 16-bit signed integer.
• int: 32-bit signed integer.
• long: 64-bit signed integer.
• float: 32-bit single-precision floating-point.
• double: 64-bit double-precision floating-point.
• char: 16-bit Unicode character.
• boolean: Represents true or false.

Non-Primitive Data Types (or Reference Types) refer to objects and include Classes, Interfaces, and Arrays. These store memory addresses of objects rather than the actual data values.