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 =
Syntax
type variableName = value;For example, if you want to store some text, you can use a String :
StringTo create a variable that should store a number, you can use int :
intYou 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:
myNumFinal 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 variableOther 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";You will learn more about data types later in this lesson.