Math Class Methods

• The Math class is part of the Java API.
• Math class methods enable the programmer to specify many common mathematical calculations.
• Methods are invoked by specifying the name of the method followed by its arguments, if any, enclosed in parentheses: ( ).
• For example, printing the square root of 900 can be accomplished as follows:

  System.out.println( Math.sqrt( 900.0 ) );

  In this instance:

  • The method name is Math.sqrt.
  • It has 1 argument: 900.0, the number whose square root is sought.
  • The type of the argument to Math.sqrt is double.
  • The type of the value returned by Math.sqrt (in this case, 30) is double
• Normally, a method (e.g., drawString) is invoked by an object (e.g., g).

  g.drawString("Send g the drawString message.", 25, 52);

• Class methods however are associated via the dot notation with a class name, in this case Math.

  Another class method that we have seen is Integer.parseInt (Integer is the class name; parseInt is the method name). Its argument is of type String; its return type is int;

  Its "inverse" class method Integer.toString, takes an argument of type int, and returns a value of type String.

• Lastly, when you invoke an applet method within the definition of an applet [sub]class, the dot notation is dropped:

  showStatus("Applet started."); // apply showStatus to this applet class (e.g., Addition).

  showStatus, the method name, is implicitly applied to the applet class in which the statement appears.

• If a method has an argument of a certain type, say int, then its argument can be any expression whose value is of that type.

  double c = 13.0, d = 3.0, e = 4.0;

  System.out.println( c + Math.sqrt( c + d * f ) );

  prints 18. At the time the statement is executed, Java:

  • substitutes the value of c, d, and e in the expression:

    System.out.println( 13.0 + Math.sqrt( 13.0 + 3.0 * 4.0 ) );

  • evaluates the Math.sqrt argument expression:

    System.out.println(13.0 + Math.sqrt( 25 ) );

  • performs the Math.sqrt class method, substituting the returned value:

    System.out.println( 13.0 + 5.0 ); // println with an argument of type double?

  • evaluates the println argument expression:

    System.out.println( 18.0 );

  • performs the println method, sending "18" to the System.out Stream.
• Familiarize yourself with the Math class methods given on Chapter 4 of our text book:
  • abs ( x )
  • ceil ( x )
  • cos ( x )
  • exp ( x )
  • floor ( x )
  • log ( x )
  • max ( x, y )
  • min ( x, y )
  • pow ( x, y )
  • sin ( x )
  • sqrt ( x )
  • tan ( x )