What is a variable in Java?
It is defined as a container that can hold any type of data. As the name implies, we can alter the value stored in the variable.
Key Points:-
- It is a name given to the location in the memory in which we store data.
Declaration of Variable:- To declare a variable first write datatype ( type of data i.e. int,
float, char, etc.) then space (“ ”), and then write the name of the variable (Identifier).
Syntax:
datatype variable_name;
Example:
int a;
Initialization of Variable: - To initialize a variable we have to assign a value to the variable.
Syntax:
variable_name = value;
Example:
var = 12;
Example of Declaration and Initialization of the variable at once:
int a=20;
String s="Hello";
Types of Variables
Variables are of three types: Instance, Local, Static
1. Instance Variable: - Variable declared within a class but outside of any methods.
Example:
package quipohouse;
public class InstanceVariable {
int var = 10; // Declaration and initialization of instance variable
public static void main(String[] args) {
InstanceVariable c = new InstanceVariable();
System.out.println(c.var);
}
}
Output:
10
2. Local Variable: -Variable declared inside any method or block. The scope of the local variable is inside that method or block.
Example:
package quipohouse;
public class LocalVariable {
public static void main(String[] args) {
int var2 = 12; // Declaration and initialization of Local Variable
System.out.println(var2);
}
}
Output:
12
3. Static Variable:
- A variable marked with a static keyword is known as a static variable. e.g. - static int var;
- The static variable is declared inside a class but outside any method.
- The scope of the static variable is inside the class.
- We can have only one copy of the static variable of any class, independent of the number of objects we create.
- As a result, if we make any changes to a static variable in one object then it
will reflect back on another variable. - We can directly access static variables by using the class name.
- We can also access static variables without using the class name within a class inside the static block. In this scenario compiler automatically append the class name before it.
Example:
package quipohouse;
public class StaticVariable {
static int var; // Declaration of static variable
public static void main(String[] args) {
System.out.println(StaticVariable.var); // 20
System.out.println(var); // 20
}
}
Output:
0
0