public class FirstClass 
{
   int ivar;
   double dvar;
   Second s;

   public FirstClass() 
   {
      this(10);
   }

   public FirstClass(int i) 
   {
      this.ivar = i;
      dvar = 2 * iSquare();
   }

   public FirstClass(int i, double d) 
   {
      ivar = i;
      dvar = d; 
   }

   public int iSquare() {
      return ivar * ivar ;
   }

   public void setIvar(int i) {
      ivar = i;
      dvar = 10.0 * ivar;
   }

   public static void printHello() {
      System.out.println("Hello, World!");
   }

   public void printHello2() {
      System.out.println("Hello, World! (V.2, non-static)");
   }

   public double dSquare() {
      return dvar * dvar ;
   }

   public static void main ( String[] args )
   {
      FirstClass fc, fc2;

      System.out.println("This is my first class in Java");

      System.out.println("Number of argments: " + args.length);

      for ( int i = 0; i < args.length; i++ ) {
         System.out.println(args[i] + ", length of argument: " + args[i].length());
      }

      fc = new FirstClass();

      System.out.println("fc.ivar = " + fc.ivar);
      System.out.println("fc.dvar = " + fc.dvar);

      fc.ivar = fc.ivar * 2;
      System.out.println("fc.ivar = " + fc.ivar + " (after change)");

      System.out.println("fc.iSquare() = " + fc.iSquare());
      System.out.println("fc.dSquare() = " + fc.dSquare());

      fc2 = new FirstClass();
      fc2.ivar = fc2.ivar / 2;
      System.out.println("fc2.iSquare() = " + fc2.iSquare());
      System.out.println("fc2.dSquare() = " + fc2.dSquare());

      System.out.println("fc.iSquare() = " + fc.iSquare());
      System.out.println("fc.dSquare() = " + fc.dSquare());

      FirstClass.printHello();
      //FirstClass.printHello2();
      fc.printHello2();
   }
}