Java Variables

Java Variables

A variable is a container that stores a value. In Java you must always declare the type of a variable before you use it.

Declaring a variable

Use the type, a name, an equals sign, and a value:

int myNum = 5;
String name = "John";

Here int stores whole numbers and String stores text.

Changing the value

You can change a variable later by assigning a new value:

int myNum = 5;
myNum = 10;
System.out.println(myNum);

This prints 10.

Final variables

The final keyword makes a variable constant, so its value cannot be changed:

final int myNum = 15;
// myNum = 20;  this will cause an error

Naming rules

• Names are case sensitive.
• They must start with a letter, underscore _, or dollar sign $.
• Use camelCase, like myNumber, for multiple words.
• Avoid reserved keywords like int or class.

Combining declaration and use

int a = 5;
int b = 3;
int sum = a + b;
System.out.println(sum);

TL;DR

• Declare variables with a type, name, and value.
• Values can be changed unless the variable is final.
• Follow naming rules and use camelCase.