Data
Variable
Java
int age;
String name = "Sam";
Here, we are defining a variable age of type Integer and name of type String.
You can optionally initialize a variable with a value in its declaration.
Variable names are:
- Case sensitive
- Can contain letters, digits,
$
or_
- Cannot start with a digit
- Cannot be any of the reserved keywords
// Primative Data Types
boolean booleanVar = true;
byte byteVar = 12;
short shortVar = 12;
int intVar = 12;
long longVar = 12L;
float floatVar = 1.618F;
double doubleVar = 1.618;
char charVar = 'c';
// Non-Primative Data Types
String stringVar = "Hello";
int[] arrayVar = new int[7];
Data Types in Java are divided into two groups:
Primitive Data Types:
These are the most basic data types, which are:boolean
,byte
,short
,int
,long
,float
,double
,char
.Non-Primitive Data Types:
These are types that are using Primitive Types to create new Types:String
,Array
, Class object types, etc.
int status = 0;
status = "success"; // Error
Java is a Type-Safe programming language, meaning that variables can only accept values of their type.
int x, y=7, z=12;
You can define multiple variables in one statement.
Here, we are creating variables x, y, and z of type integer, and initialize y to 7 and z to 12.
int age;
age = 21;
Here, we are defining a variable age of type integer first and assign a value 21 to it.