Variables and Literals in Java
In this tutorial, we will learn about Java variables and literals with the help of examples.
A variable is a location in memory (storage area) to hold data.
To indicate the storage area, each variable should be given a unique name (identifier). Learn more about Java identifiers.
Here’s how we create a variable in Java,
int speedLimit = 80;
Here, speedLimit
is a variable of int
data type and we have assigned value 80 to it.
The int data type suggests that the variable can only hold integers. To learn more, visit Java data types.
In the example, we have assigned value to the variable during declaration. However, it’s not mandatory.
You can declare variables and assign variables separately. For example,
int speedLimit;
speedLimit = 80;
Note : Java is a statically-typed language. It means that all variables must be declared before they can be used.
The value of a variable can be changed in the program, hence the name variable. For example,
int speedLimit = 80;
... .. ...
speedLimit = 90;
Here, initially, the value of speedLimit
is 80. Later, we changed it to 90.
However, we cannot change the data type of a variable in Java within the same scope.
What is the variable scope?
Don’t worry about it for now. Just remember that we can’t do something like this:
int speedLimit = 80;
... .. ...
float speedLimit;
To learn more, visit: Can I change declaration type for a variable in Java?
Java programming language has its own set of rules and conventions for naming variables. Here’s what you need to know:
age
and AGE
are two different variables. For example,int age = 24;
int AGE = 25;
System.out.println(age); // prints 24
System.out.println(AGE); // prints 25
int age; // valid name and good practice
int _age; // valid but bad practice
int $age; // valid but bad practice
int 1age; // invalid variables
int my age; // invalid variables
Here, is we need to use variable names having more than one word, use all lowercase letters for the first word and capitalize the first letter of each subsequent word. For example, myAge
.
score
, number
, level
makes more sense than variable names such as s
,n
, and l
.speed
rather than SPEED
, or sPEED
.There are 4 types of variables in Java programming language:
If you are interested to learn more about it now, visit Java Variable Types.
Literals are data used for representing fixed values. They can be used directly in the code. For example,
int a = 1;
float b = 2.5;
char c = 'F';
Here, 1
, 2.5
, and 'F'
are literals.
Here are different types of literals in Java.
In Java, boolean literals are used to initialize boolean data types. They can store two values: true and false. For example,
boolean flag1 = false;
boolean flag2 = true;
Here, false
and true
are two boolean literals.
An integer literal is a numeric value(associated with numbers) without any fractional or exponential part. There are 4 types of integer literals in Java:
For example:
// binary
int binaryNumber = 0b10010;
// octal
int octalNumber = 027;
// decimal
int decNumber = 34;
// hexadecimal
int hexNumber = 0x2F; // 0x represents hexadecimal
// binary
int binNumber = 0b10010; // 0b represents binary
In Java, binary starts with 0b, octal starts with 0, and hexadecimal starts with 0x.
Note : Integer literals are used to initialize variables of integer types
like byte
, short
, int
, and long
.
A floating-point literal is a numeric literal that has either a fractional form or an exponential form. For example,
class Main {
public static void main(String[] args) {
double myDouble = 3.4;
float myFloat = 3.4F;
// 3.445*10^2
double myDoubleScientific = 3.445e2;
System.out.println(myDouble); // prints 3.4
System.out.println(myFloat); // prints 3.4
System.out.println(myDoubleScientific); // prints 344.5
}
}
Note : The floating-point literals are used to initialize float
and double
type variables.
Character literals are unicode character enclosed inside single quotes. For example,
char letter = 'a';
Here, a
is the character literal.
We can also use escape sequences as character literals. For example, \ (backspace), \ (tab), \n (new line), etc.
A string literal is a sequence of characters enclosed inside double-quotes. For example,
String str1 = "Java Programming";
String str2 = "Javaistic";
Here, Java Programming
and Javaistic
are two string literals.