//  MathDemo.java  (c) 2005 Kari Laitinen

//  http://www.naturalprogramming.com

//  2005-05-05  File created.
//  2005-05-30  Last modification.

//  This program demonstrates the use of the static mathematical
//  methods in class Math.

class MathDemo
{
   static final double  EARTH_RADIUS_IN_KILOMETERS  =  6379  ;

   public static void main( String[] not_in_use )
   {
      double  an_angle_in_radians  =  Math.toRadians( 45 ) ;

      double  sine_of_an_angle  =  Math.sin( an_angle_in_radians ) ;

      System.out.print( "\n The sine of an angle of 45 degrees is "
                     +  sine_of_an_angle  +  "\n" ) ;

      double  diameter_of_the_earth  =
                  2  *  Math.PI  *  EARTH_RADIUS_IN_KILOMETERS ;

      //  Because our planet Earth is not exactly a ball, the
      //  diameters and areas calculated below are approximate.

      System.out.printf( "\n Earth diameter in kilometers:   %15.0f", 
                         diameter_of_the_earth ) ;

      System.out.printf( "\n Earth diameter in miles:        %15.0f",
                         diameter_of_the_earth / 1.6093 ) ;

      double  surface_area_of_the_earth  =
                  4  *  Math.PI  *  Math.pow( EARTH_RADIUS_IN_KILOMETERS, 2 );

      System.out.printf( "\n Earth area in square kilometers:%15.0f",
                         surface_area_of_the_earth ) ;
      System.out.printf( "\n Earth area in square miles:     %15.0f\n",
                         surface_area_of_the_earth / Math.pow( 1.6093, 2 ) );

      int  a_random_integer  =  (int) ( Math.random() * 50 ) ;

      System.out.printf( "\n And here is a random integer in the range "
                      +  "from 0 to 49:  "  +  a_random_integer  +  "\n\n" ) ;


      //  THE REST OF THE LINES ARE NOT SHOWN IN THE BOOK!

      //  Method Math.round() is able round numbers as humans do.
      //  Otherwise, computers always round downwards.

      System.out.print( "\n ((int) 34.56 ) evaluates to      "
                      + ( (int) 34.56 )
                      + "\n Math.round( 34.56 ) evaluates to "
                      + Math.round( 34.56 )
                      + "\n Math.rint( 34.56 ) evaluates to  "
                      + Math.rint( 34.56 )  +  "\n" ) ;

      System.out.print( "\n ((int) 34.50 ) evaluates to      "
                      + ( (int) 34.50 )
                      + "\n Math.round( 34.50 ) evaluates to "
                      + Math.round( 34.50 )
                      + "\n Math.rint( 34.50 ) evaluates to  "
                      + Math.rint( 34.50 )  +  "\n" ) ;

   }
}