iTechtalk

prashant

Package-java.lang.Math

Another class you will refer to often, especially when programming games, is the Math class. Rather than instantiating this class, you will desire to use its static methods to perform many different mathematical operations.

The Math class gives two handy constant values for use in your programs: the natural logarithm base e and the value of pi—the ratio of the circumference of a circle to its diameter. The following demonstrates how you can use pi to calculate the area of a circle:

double radius = 4.5;
double area = Math.PI * radius * radius;
System.out.println("The area of a circle with radius " + radius + " is " + area);

The output would be

The area of a circle with radius 4.5 is 63.61725123519331

Other utilities found within the Math class consist of basic trigonometry and degree conversion methods. This contains the sine, arcsine, cosine, arccosine, tangent, and arctangent of an angular measurement in radians. You can also rapidly convert a degree measurement to radians and vice versa using the toRadians, and toDegrees methods, respectively:

double degrees = 45.0;
double radians = Math.toRadians(degrees);
System.out.println(degrees + " degrees = " + radians + " radians");
System.out.println("So, " + radians + " radians = " +Math.toDegrees(radians) + "degrees!");

This will output

45.0 degrees = 0.7853981633974483 radians
So, 0.7853981633974483 radians = 45.0 degrees!

Maybe that wasn’t the most interesting example, but it is a useful construct nonetheless. A possibly more interesting method found in the Math class is the random method. There is no such thing as a truly random number on digital computers since on computers random numbers are computed algorithmically with deterministic algorithms and their sequences can be predicted and reproduced. However, the way in which Java pseudorandomly calculates random numbers is sufficient for your requirements.

The Math random method creates a double value greater than or equal to 0.0 and less than 1.0. Its magnitude is always positive, and the values it chooses usually fall within a uniform distribution of that range. The following code snippet creates 25 Integer objects whose values range between 50 and 100:

Integer[] values = new Integer[20];
for(int i = 0; i < values.length; i++)
{
values[i] = new Integer((int)(50.0 + (Math.random()*51.0)));
}
System.out.println(Arrays.asList(values));

If you feel that the code that chooses the random value looks too congested, feel free to break it up into several steps. Output for this code may look like the following:

[87, 65, 99, 67, 62, 65, 95, 69, 96, 92, 50, 98, 53, 100, 69, 51, 95, 54, 76, 55]

There are also a number of other Math routines, summarized by the following:

1) Math.abs: Returns the absolute value of the sent number.

2) Math.ceil: Returns the ceiling of the sent double value.

3) Math.exp: Returns the value of e raised to the sent double value. This is equivalent to System.out.println(Math.pow(Math.E, value));

4) Math.floor: Returns the floor value of the sent double.

5) Math.max: Returns the greater of the two sent parameters.

6) Math.min: Returns the lesser of the two sent parameters.

7) Math.pow: Returns the first value raised to the power of the second.

8) Math.round: For float types, returns the closest int value. For doubles, returns the closest long value.

9) Math.sqrt: Returns the rounded positive square root of the sent double value.