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Variables are containers for storing data values
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 quotesint - stores integers (whole numbers), without decimals, such as 123 or -123float - stores floating point numbers, with decimals, such as 19.99 or -19.99char - stores single characters, such as
'a' or 'B'. Char values are surrounded by single quotesboolean - stores values with two states:
true or falseTo 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:
Create a variable called name of type String and assign it the value "John":
String name = "John";
System.out.println(name);
To create a variable that should store a number, look at the following example:
Create a variable called myNum of type int and assign it the value 15:
int myNum = 15;
System.out.println(myNum);
You can also declare a variable without assigning the value, and assign the value later:
Note that if you assign a new value to an existing variable, it will overwrite the previous value:
Change the value of myNum from 15 to 20:
int myNum = 15;
myNum = 20; // myNum is now 20
System.out.println(myNum);
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
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";
You will learn more about data types in the next section.