



Math Class


Java's Math class contains a collection of methods, and two constants, that
support mathematical computation. The class is final, so you cannot extend
it. The constructor is private, so you cannot create an instance. Fortunately,
the methods and constants are static, so they can be accessed through the
class name without having to construct a Math object.
The two constants of the Math class are:

Math.PI
Math.E

There are a bunch of methods supporting trigonometric operations, rounding
operations, absolute value, etc. 

Math Methods In Action: Here's a sample program showing a
couple of the math methods in action:


import java.awt.*;
import java.applet.*;

public class mathStuff extends Applet{
  public void init(){
    setBackground(Color.yellow);
    add(new Label("Math.sqrt(81)="+Math.sqrt(81)));
    add(new Label("Math.sin(33)="+Math.sin(33)));
    add(new Label("Math.abs(-44)="+Math.abs(-44)));
    add(new Label("Math.ceil(4.44)="+Math.ceil(4.44)));
    add(new Label("Math.floor(4.44)="+Math.floor(4.44)));
    add(new Label("Math.round (4.44)="+Math.round(4.44)));
    add(new Label("Math.random()="+Math.random()));
    add(new Label("Math.max(88,99)="+Math.max(88,99)));
    add(new Label("Math.min(77,33)="+Math.min(77,33)));
  }
}





Circle Operations: The following sample applet demonstrates
a couple of things. First of all, a class called circle is created. The
applet class, called circ, contains an instance of this class. You will
notice the line

c=new circle(9);
This line calls the constructor of the circle class. From then on the
variables and methods in the circle class can be used quite easily. For
instance, c.radius produces the radius and c.diameter() returns the
diameter. Notice the difference between how variables and methods are
accessed (variables don't have parenthesis).
You should realize that when you compile the following file, two class
files will be created.

import java.awt.*;
import java.applet.*;

public class circ extends Applet{
  circle c;

  public void init(){
    c=new circle(9);
    setBackground(Color.yellow);
  }

  public void paint(Graphics g){
    g.drawString("RADIUS: "+c.radius, 10,20);
    g.drawString("DIAMETER: "+c.diameter(), 10, 40);
    g.drawString("CIRCUMFERENCE: "+c.circumference(), 10, 60);
    g.drawString("AREA: "+c.area(), 10, 80);
  }
}

class circle{
  int radius;
  
  circle(int r){
    radius = r;
  }

  int diameter(){
    return radius*2;
  }

  double circumference(){
    return Math.round(Math.PI*2*radius);
  }
  
  double area(){
    return Math.round(Math.PI*radius*radius);
  }
}





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Here's another example applet which might be interesting to look at:

FINANCIAL PLANNING - COMPOUND INTEREST APPLET


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Assignment: The Pythagorean Theorem works something like this:
If you know the the lengths of the two lines adjacent to the right angle of
a right triangle, then you can calculate its hypotenuse using the following
formula:
    hypotenuse=square_root(side1*side1+side2*side2);

For this assignment you will create a class called rtTri which represents
a right triangle. You will create a second class which uses the rtTri class
to find the hypotenuse of a right triangle from two numbers supplied by the
user to the applet.
 Be sure to use relevant methods from the Math
class to help you with this program.