Variable Types in Java

Introduction

 

A variable specifies a memory location that contains data. The data can be numbers, characters and so on. There are three types of variables in Java:

1. Local variables 
2. Instance variables 
3. Class variables

Local variables

• A method uses local variables for storing its temporary state.
• Generally, these are declared inside the methods, constructors or blocks of code.
• These should always be declared and initialized before their use.
• We cannot access local variables anywhere other than the specific methods, constructors or blocks of code in which they are declared.
• When the method is executed completely, these local variables are destroyed.

Example:

package myclass1;
class Myclass1 {
 public void classStrength() {
  int strength = 100;
  strength = strength - 10;
  System.out.println("Class strength is : " + strength);
 }
 public static void main(String args[]) {
  Myclass1 count = new Myclass1();
  count.classStrength();
 }
}

Output:

 

 

 

Instance variables

• These are also known as non-static variables.
• These are declared inside a class, but outside a method, constructor or a block of code.
• Instance variables have a default value.
• These are created and destroyed when the object is created and destroyed respectively.
• Inside the class these can be accessed directly by calling their names.
• Instance variables can be accessed by all methods, constructors or blocks of code in the same class.

Example:

package myclass1;
class Myclass1 {
 public String location;
 private int id;
 public Myclass1(String Location) {
  location = Location;
 }
 public void id(int classid) {
  id = classid;
 }
 public void Location() {
  System.out.println("Location : " + location);
  System.out.println("id :" + id);
 }
 public static void main(String args[]) {
  Myclass1 scl = new Myclass1("ndl");
  scl.id(10090);
  scl.Location();
 }
}

Output:

 

Class variables

• These are also known as static variables.
• These are declared inside a class with a static keyword, but outside a method, constructor or a block of code.
• These variables are created and destroyed when the program starts and ends respectively.
  
• Class variables also have a default value.
• These variables can be accessed just by referring to them with the class name.

Example:

package myclass1;
class Myclass1 {
 private static int rollno;
 public static final String CLASS = "class topper";
 public static void main(String args[]) {
  rollno = 10;
  System.out.println(CLASS + " roll no is :" + rollno);
 }
}

Output:

 

Summary

 

This article will introduce you to the various types of variables in Java and their properties.