I'm still having trouble understandig the static keyword, what difference does it make to a variable?

Hi Kristoffer,

This is a tricky concept to get your head round, I agree!

The static keyword, when used on a member variable is associated with the class not the objects/instances of the class. So, you can use it when no objects exist.

public class Steve{
  public static String name = "Steve";
}

Here's a class definition. In your code you can access this variable:

// somehwere in your code
System.out.println(Steve.name);

You call it off the class name, hence the capitalized Steve.

The variable is common across all instances too. So, you can do this:

public class Steve{
  public static String name = "Steve";
  public static int howMany = 0;

  public Steve(){
    // I'm a constructor
    howMany++;
  }
}

So, here in the constructor, we increment the howMany variable. This will count how many instances of Steve exist (one's enough, trust me!). This means every instance of Steve will contain the same value in howMany So:

Steve oneSteve = new Steve();
Steve twoSteve = new Steve();
Steve threeSteve = new Steve();

Every instance here will have the value 3 held in howMany. oneSteve.howMany and threeSteve.howMany will both hold 3. This means you can count instances of your class, or how many times the constructor has run, anyway.

I hope that helps!

Steve.