Data Types, Variables in Java

1) Data Types, Variables, and Constants in Java

Data Types

In Java, data types define the kind of data a variable can hold. They are categorized into two types:

• Primitive Data Types: These are predefined by the language
  • byte: 8-bit integer (-128 to 127)
  • short: 16-bit integer (-32,768 to 32,767)
  • int: 32-bit integer (-2^31 to 2^31-1)
  • long: 64-bit integer (-2^63 to 2^63-1)
  • float: Single-precision 32-bit floating-point
  • double: Double-precision 64-bit floating-point
  • char: 16-bit Unicode character
  • boolean: Represents true or false
• Reference Data Types: Used to store objects like arrays, strings, or user-defined classes.

Variables

A variable is a storage unit used to hold data values. Variables in Java must be declared with a type.

data_type variable_name = value;

int age = 25;
double price = 99.99;
char grade = 'A';
boolean isActive = true;

Constants

Constants are unchanging values that remain the same once defined. Declared using the final keyword.

final data_type CONSTANT_NAME = value;

final double PI = 3.14159;
final int MAX_USERS = 100;