A variable in Java is a named location in memory that holds a value. Variables are used to store data that can be used throughout a program.
There are three main types of variables in Java:
- Local variables: These variables are declared within a method, constructor, or block of code. They are only accessible within the scope in which they are defined.
- Instance variables: These variables are declared within a class but outside any method, constructor, or block of code. They are associated with individual instances (objects) of the class.
- Static variables: These variables are declared with the
static
keyword within a class but outside any method, constructor, or block of code. They are associated with the class itself rather than with instances of the class.
Example of local variable
public class LocalVariableExample {
public static void main(String[] args) {
int age; // local variable
age = 25;
System.out.println("My age is: " + age);
}
}
Output;
My age is: 25
Example of instance variable
public class InstanceVariableExample {
// instance variable
String name;
public static void main(String[] args) {
InstanceVariableExample obj = new InstanceVariableExample();
System.out.println("My name is: " + obj.name);
}
}
Output:
My name is: null
Example of static variable
public class StaticVariableExample {
// static variable
static int count = 0;
public static void main(String[] args) {
StaticVariableExample obj1 = new StaticVariableExample();
obj1.count++;
StaticVariableExample obj2 = new StaticVariableExample();
obj2.count++;
StaticVariableExample obj3 = new StaticVariableExample();
obj3.count++;
System.out.println("Total objects created: " + count);
}
}
Output:
Total objects created: 3
Can you answer why the output is 3?
I would love to hear your answer in the comment section below.
Thank you
Frequently Asked Questions
What is a variable in Java?
A variable in Java is a named storage location used to store data temporarily during program execution.
What are the rules for naming variables in Java?
Variable names must start with a letter, underscore, or dollar sign, followed by letters, digits, underscores, or dollar signs. They are case-sensitive and cannot be Java keywords.
How do I declare a variable in Java?
To declare a variable in Java, specify its data type followed by the variable name, like this: int myNumber;
.
What is the scope of a variable in Java?
The scope of a variable determines where it can be accessed. Variables declared inside a block have local scope, while those declared in a class have class scope.
How do I assign a value to a variable in Java?
You can assign a value to a variable using the assignment operator (=
), like this: myNumber = 42;
.