// SquareTest class

public class SquareTest
{
   public static void main(String[] args)
   {
      Square block = new Square();
      Square box = new Square(3);
      block.setWidth(4);
      System.out.println(box.getWidth());    // 3
      System.out.println(block.computeArea());  // 16
      System.out.println(box.computePerimeter());  // 12
   }
}

// Square class

class Square
{
    // ********************************* constructors

    // default constructor
    public Square()
    {
        myWidth = 0;
    }
    
    // "other" constructor
    public Square(double width)
    {   
        myWidth = width;
    }
    
    // ********************************* accessor method
    public double getWidth()
    {
        return myWidth;
    }
    
    // ********************************* modifier methods
    public void setWidth(double width)
    {
        myWidth = width;
    }
        
    // ********************************* "interesting" methods
    public double computeArea()
    {
        return myWidth * myWidth;
    }
    
    public double computePerimeter()
    {
	return myWidth * 4;
    }
    
    // ********************************* instance variables (properties)
    private double myWidth;
}