Variables and Constants

Variables

Used to store data values in memory.

Types of Variables:

1. Class Variables (static) – one copy for all objects.

2. Instance Variables – different for each object.

3. Local Variables – exist only within a method or block.

Constants

• Value cannot be changed after declaration.

• Declared using static final keywords.

Example:

static final double PI = 3.14159;

Data Types in Java

1. Primitive Data Types

• byte, short, int, long

• float, double

• char, boolean

2. Non-Primitive Data Types

• String – Sequence of characters (immutable).

Array – Fixed-size collection of elements of the same type.