Variables

Variables in Java

A variable is a name given to a memory location used to store data.

• Value can change during execution
• Represents memory location
• Must be declared before use

Types of Variables

• Primitive
• Reference

Primitive Variables: Store actual values.

Types: int, byte, short, long, float, double, boolean, char

int x = 10;
float f = 5.5f;

Reference Variables: Store object reference.

Student s = new Student();

Program Output

Variables are also classified as Local, Instance, and Static.

Local Variables

• Declared inside methods
• No default value
• Must initialize before use
• Stored in stack memory

int x;
System.out.println(x); // error

Instance Variables

• Declared inside class but outside methods
• Each object has its own copy
• Default values provided by JVM

class Student {
  int id;
}

Static Variables

• Declared using static keyword
• Shared among all objects
• Stored in method area

class Test {
  static int count = 0;
}

Comparison Table

Type	Scope	Default Value	Memory
Local	Method	No	Stack
Instance	Object	Yes	Heap
Static	Class	Yes	Method Area

Example Program

class Test {
  static int a = 10;
  int b = 20;

  public static void main(String[] args) {
    int c = 30;
    System.out.println(a + " " + c);
  }
}

Summary

• Primitive → stores value
• Reference → stores address
• Local → no default value
• Instance → object-level
• Static → class-level shared