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, you must specify the type and assign it a value:

type variableName = value;

Where type is one of Java's types (such as int or String), and variableName is the name of the variable (such as x or name). The equal sign is used to assign values to the variable.

To create a variable that should store text, look at the following example:

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

To create a variable that should store a number, look at the following example:

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

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

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:

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):

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:

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

Video: Java Variables