Java Variables

Java Variables

Variables are containers for storing data values.

In Java, there are different types of variables, for example:

• String - stores text, such as "Hello". String values are surrounded by double quotes
• int - stores integers (whole numbers), without decimals, such as 123 or -123
• float - stores floating point numbers, with decimals, such as 19.99 or -19.99
• char - stores single characters, such as 'a' or 'B'. Char values are surrounded by single quotes
• boolean - stores values with two states: true or false

Declaring (Creating) Variables

To create a variable in Java, you need to:

• Choose a type (like int or String)
• Give the variable a name (like x, age, or name)
• Optionally assign it a value using =

Here's the basic syntax:

Syntax

type variableName = value;

For example, if you want to store some text, you can use a String:

Example

String name = "John";
System.out.println(name);

To create a variable that should store a number, you can use int:

Example

int myNum = 15;
System.out.println(myNum);

You can also declare a variable without assigning the value, and assign the value later:

Example

int myNum;
myNum = 15;
System.out.println(myNum);

Note that if you assign a new value to an existing variable, it will overwrite the previous value:

Example

int myNum = 15;
myNum = 20;  // myNum is now 20
System.out.println(myNum);

Final Variables

If you don't want others (or yourself) to overwrite existing values, use the final keyword (this will declare the variable as "final" or "constant", which means unchangeable and read-only):

Example

final int myNum = 15;
myNum = 20;  // will generate an error: cannot assign a value to a final variable

Other Types

A demonstration of how to declare variables of other types:

Example

int myNum = 5;
float myFloatNum = 5.99f;
char myLetter = 'D';
boolean myBool = true;
String myText = "Hello";

Note: You will learn more about data types in the next section.