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Java Masterclass for Software Developers

Undefined Variables of a Class Type

In this lesson, we will look at what happens when you forget to initialize your variables.

We'll cover the following...

Two instances of the class Square

Let’s create two Square objects using the class Square given in the previous chapter. The following program attempts this task but includes a common mistake that anyone might make. Do you see the mistake?

Java
public class DemoTwoSquares
{
   public static void main(String[] args)
   {
      Square smallSquare, bigSquare;
      smallSquare.setSide(1);
      bigSquare.setSide(100);
		  
      System.out.println("Small square: side = " +
                          smallSquare.getSide() + ", " +
                         "area = " + smallSquare.getArea());
      System.out.println("Big square: side = " +
                          bigSquare.getSide() + ", " +
                         "area = " + bigSquare.getArea());
	} // End main
} // End DemoTwoSquares

You ...