Revisions to What are the differences between class variables and instance variables in Java? [closed]

Commonmark migration

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edited Jun 16, 2020 at 10:01

1

They both are member variables, meaning that both are associated with a class. Now of course, there are differences between the two:

Instance variables:

These variables belong to the instance of a class, thus an object. And every instance of that class (object) has it's own copy of that variable. Changes made to the variable don't reflect in other instances of that class.

public class Product {
    public int Barcode;
}

Class variables:

These are also known as static member variables and there's only one copy of that variable that is shared with all instances of that class. If changes are made to that variable, all other instances will see the effect of the changes.

public class Product {
    public static int Barcode;
}

Full example:

// INSTANCE VARIABLE
public class Main {

    public static void main(String[] args) {
    
        Product prod1 = new Product();
        prod1.Barcode = 123456;

        Product prod2 = new Product();
        prod2.Barcode = 987654;

        System.out.println(prod1.Barcode);
        System.out.println(prod2.Barcode);
    }
}

public class Product {
    public int Barcode;
}

The output will be:

Now, change the instance variable to a class variable by making it static:

//CLASS VARIABLE
public class Main {

    public static void main(String[] args) {
    
        Product prod1 = new Product();
        prod1.setBarcode(123456);
        Product prod2 = new Product();
        prod2.setBarcode(987654);

        System.out.println(prod1.getBarcode());
        System.out.println(prod2.getBarcode());
    }
}

public class Product {

    public static int Barcode;

    public int getBarcode() {
        return Barcode;
    }

    public void setBarcode(int value){
        Barcode = value;
    }
}

I used non-static methods to get and set the value of Barcode to be able to call it from the object and not from the class. The output will be following:

They both are member variables, meaning that both are associated with a class. Now of course, there are differences between the two:

Instance variables:

These variables belong to the instance of a class, thus an object. And every instance of that class (object) has it's own copy of that variable. Changes made to the variable don't reflect in other instances of that class.

public class Product {
    public int Barcode;
}

Class variables:

These are also known as static member variables and there's only one copy of that variable that is shared with all instances of that class. If changes are made to that variable, all other instances will see the effect of the changes.

public class Product {
    public static int Barcode;
}

Full example:

// INSTANCE VARIABLE
public class Main {

    public static void main(String[] args) {
    
        Product prod1 = new Product();
        prod1.Barcode = 123456;

        Product prod2 = new Product();
        prod2.Barcode = 987654;

        System.out.println(prod1.Barcode);
        System.out.println(prod2.Barcode);
    }
}

public class Product {
    public int Barcode;
}

The output will be:

Now, change the instance variable to a class variable by making it static:

//CLASS VARIABLE
public class Main {

    public static void main(String[] args) {
    
        Product prod1 = new Product();
        prod1.setBarcode(123456);
        Product prod2 = new Product();
        prod2.setBarcode(987654);

        System.out.println(prod1.getBarcode());
        System.out.println(prod2.getBarcode());
    }
}

public class Product {

    public static int Barcode;

    public int getBarcode() {
        return Barcode;
    }

    public void setBarcode(int value){
        Barcode = value;
    }
}

I used non-static methods to get and set the value of Barcode to be able to call it from the object and not from the class. The output will be following:

They both are member variables, meaning that both are associated with a class. Now of course, there are differences between the two:

Instance variables:

These variables belong to the instance of a class, thus an object. And every instance of that class (object) has it's own copy of that variable. Changes made to the variable don't reflect in other instances of that class.

public class Product {
    public int Barcode;
}

Class variables:

These are also known as static member variables and there's only one copy of that variable that is shared with all instances of that class. If changes are made to that variable, all other instances will see the effect of the changes.

public class Product {
    public static int Barcode;
}

Full example:

// INSTANCE VARIABLE
public class Main {

    public static void main(String[] args) {
    
        Product prod1 = new Product();
        prod1.Barcode = 123456;

        Product prod2 = new Product();
        prod2.Barcode = 987654;

        System.out.println(prod1.Barcode);
        System.out.println(prod2.Barcode);
    }
}

public class Product {
    public int Barcode;
}

The output will be:

Now, change the instance variable to a class variable by making it static:

//CLASS VARIABLE
public class Main {

    public static void main(String[] args) {
    
        Product prod1 = new Product();
        prod1.setBarcode(123456);
        Product prod2 = new Product();
        prod2.setBarcode(987654);

        System.out.println(prod1.getBarcode());
        System.out.println(prod2.getBarcode());
    }
}

public class Product {

    public static int Barcode;

    public int getBarcode() {
        return Barcode;
    }

    public void setBarcode(int value){
        Barcode = value;
    }
}

I used non-static methods to get and set the value of Barcode to be able to call it from the object and not from the class. The output will be following:

added 92 characters in body

Source Link

edited Aug 12, 2015 at 8:24

Abbas

543
3
10

They both are member variables, meaning that both are associated with a class. Now of course, there are differences between the two:

Instance variables:

These variables belong to the instance of a class, thus an object. And every instance of that class (object) has it's own copy of that variable. Changes made to the variable don't reflect in other instances of that class.

public class Product {
    public int Barcode;
}

Class variables:

These are also known as static member variables and there's only one copy of that variable that is shared with all instances of that class. If changes are made to that variable, all other instances will see the effect of the changes.

public class Product {
    public static int Barcode;
}

Full example:

// INSTANCE VARIABLE
public class Main {

    public static void main(String[] args) {
    
        Product prod1 = new Product();
        prod1.Barcode = 123456;

        Product prod2 = new Product();
        prod2.Barcode = 987654;

        System.out.println(prod1.Barcode);
        System.out.println(prod2.Barcode);
    }
}

public class Product {
    public int Barcode;
}

The output will be:

Now, change the instance variable to a class variable by making it static:

//CLASS VARIABLE
public class Main {

    public static void main(String[] args) {
    
        Product prod1 = new Product();
        Productprod1.Barcode = 123456;
setBarcode(123456);
        Product prod2 = new Product();
        Productprod2.Barcode = 987654;setBarcode(987654);

        System.out.println(prod1.getBarcode());
        System.out.println(prod2.getBarcode());
    }
}

public class Product {

    public static int Barcode;

    public int getBarcode() {
        return Barcode;
    } 

    public void setBarcode(int value){
        Barcode = value;
    }
}

I used a non-static methodmethods to get and set the value of Barcode to be able to call it from the object and not from the class. The output will be following:

They both are member variables, meaning that both are associated with a class. Now of course, there are differences between the two:

Instance variables:

These variables belong to the instance of a class, thus an object. And every instance of that class (object) has it's own copy of that variable. Changes made to the variable don't reflect in other instances of that class.

public class Product {
    public int Barcode;
}

Class variables:

These are also known as static member variables and there's only one copy of that variable that is shared with all instances of that class. If changes are made to that variable, all other instances will see the effect of the changes.

public class Product {
    public static int Barcode;
}

Full example:

// INSTANCE VARIABLE
public class Main {

    public static void main(String[] args) {
    
        Product prod1 = new Product();
        prod1.Barcode = 123456;

        Product prod2 = new Product();
        prod2.Barcode = 987654;

        System.out.println(prod1.Barcode);
        System.out.println(prod2.Barcode);
    }
}

public class Product {
    public int Barcode;
}

The output will be:

Now, change the instance variable to a class variable by making it static:

//CLASS VARIABLE
public class Main {

    public static void main(String[] args) {
    
        Product prod1 = new Product();
        Product.Barcode = 123456;

        Product prod2 = new Product();
        Product.Barcode = 987654;

        System.out.println(prod1.getBarcode());
        System.out.println(prod2.getBarcode());
    }
}

public class Product {

    public static int Barcode;

    public int getBarcode() {
        return Barcode;
    }
}

I used a non-static method to get the value of Barcode to be able to call it from the object and not from the class. The output will be following:

They both are member variables, meaning that both are associated with a class. Now of course, there are differences between the two:

Instance variables:

These variables belong to the instance of a class, thus an object. And every instance of that class (object) has it's own copy of that variable. Changes made to the variable don't reflect in other instances of that class.

public class Product {
    public int Barcode;
}

Class variables:

These are also known as static member variables and there's only one copy of that variable that is shared with all instances of that class. If changes are made to that variable, all other instances will see the effect of the changes.

public class Product {
    public static int Barcode;
}

Full example:

// INSTANCE VARIABLE
public class Main {

    public static void main(String[] args) {
    
        Product prod1 = new Product();
        prod1.Barcode = 123456;

        Product prod2 = new Product();
        prod2.Barcode = 987654;

        System.out.println(prod1.Barcode);
        System.out.println(prod2.Barcode);
    }
}

public class Product {
    public int Barcode;
}

The output will be:

Now, change the instance variable to a class variable by making it static:

//CLASS VARIABLE
public class Main {

    public static void main(String[] args) {
    
        Product prod1 = new Product();
        prod1.setBarcode(123456);
        Product prod2 = new Product();
        prod2.setBarcode(987654);

        System.out.println(prod1.getBarcode());
        System.out.println(prod2.getBarcode());
    }
}

public class Product {

    public static int Barcode;

    public int getBarcode() {
        return Barcode;
    } 

    public void setBarcode(int value){
        Barcode = value;
    }
}

I used non-static methods to get and set the value of Barcode to be able to call it from the object and not from the class. The output will be following:

deleted 76 characters in body

Source Link

edited Aug 12, 2015 at 8:12

Abbas

543
3
10

public class Product
  {
    public int Barcode;
}

public class Product
  {
    public static int Barcode;
}

Full example:

This is written in C# but it will make things clear.

// INSTANCE VARIABLE
public class Program
Main { 

    public static void Mainmain(String[] args) {
    {
        Product prod1 = new Product();
        prod1.Barcode = 123456; 

        Product prod2 = new Product();
        prod2.Barcode = 987654;

        ConsoleSystem.WriteLineout.println(prod1.Barcode);
        ConsoleSystem.WriteLineout.println(prod2.Barcode);
 
        Console.ReadKey();
    }
}

public class Product
  {
    public int Barcode;
}

//CLASS VARIABLE
public class Program
Main { 

    public static void Mainmain(string[]String[] args) {
    {
        Product prod1 = new Product();
        Product.Barcode = 123456; 

        Product prod2 = new Product();
        Product.Barcode = 987654;

        ConsoleSystem.WriteLineout.println(prod1.GetBarcodegetBarcode());
        ConsoleSystem.WriteLineout.println(prod2.GetBarcodegetBarcode());
 
        Console.ReadKey();
    }
}

public class Product
  { 

    public static int Barcode;

    public int GetBarcodegetBarcode()
    {
        return Barcode;
    }
}

public class Product
 {
    public int Barcode;
}

public class Product
 {
    public static int Barcode;
}

Full example:

This is written in C# but it will make things clear.

// INSTANCE VARIABLE
public class Program
{
    public static void Main()
    {
        Product prod1 = new Product();
        prod1.Barcode = 123456;
        Product prod2 = new Product();
        prod2.Barcode = 987654;

        Console.WriteLine(prod1.Barcode);
        Console.WriteLine(prod2.Barcode);
 
        Console.ReadKey();
    }
}

public class Product
 {
    public int Barcode;
}

//CLASS VARIABLE
public class Program
{
    public static void Main(string[] args)
    {
        Product prod1 = new Product();
        Product.Barcode = 123456;
        Product prod2 = new Product();
        Product.Barcode = 987654;

        Console.WriteLine(prod1.GetBarcode());
        Console.WriteLine(prod2.GetBarcode());
 
        Console.ReadKey();
    }
}

public class Product
 {
    public static int Barcode;

    public int GetBarcode()
    {
        return Barcode;
    }
}

public class Product {
    public int Barcode;
}

public class Product {
    public static int Barcode;
}

Full example:

// INSTANCE VARIABLE
public class Main { 

    public static void main(String[] args) {
    
        Product prod1 = new Product();
        prod1.Barcode = 123456; 

        Product prod2 = new Product();
        prod2.Barcode = 987654;

        System.out.println(prod1.Barcode);
        System.out.println(prod2.Barcode);
    }
}

public class Product {
    public int Barcode;
}

//CLASS VARIABLE
public class Main { 

    public static void main(String[] args) {
    
        Product prod1 = new Product();
        Product.Barcode = 123456; 

        Product prod2 = new Product();
        Product.Barcode = 987654;

        System.out.println(prod1.getBarcode());
        System.out.println(prod2.getBarcode());
    }
}

public class Product { 

    public static int Barcode;

    public int getBarcode() {
        return Barcode;
    }
}

Source Link

created Aug 12, 2015 at 7:41

Abbas

543
3
10

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