the Math class

•Java provides certain math functions for us. The Math class contains methods and constants that can be very useful.

•The Math class is like the String class; it is used so often that it is automatically imported.

AP methods in Math classMethod Return type Returns

Math.sqrt(x) double square root of x (>=0)

Math.pow(x,y) double xy

Math.abs(x) double or int absolute value of x

Math.random() double returns a random value >= 0 and < 1

Useful variables in Math class

Math.PI double gives a close approx to pi

OTHERS ARE FOUND AT THE API HERE

Static methods

• The Math class contains static methods and static fields.

• This means that the method does not operate on a particular object.

• You do not instantiate an object of the Math class in order to use the methods of the Math class.

• You invoke the square root method by– Math.sqrt(4)

Examplepublic static void main(String[] args) {

System.out.println(Math.sqrt(16));System.out.println(Math.random());System.out.println((int)(Math.random()*3+1));System.out.println(Math.abs(-5.1));

System.out.println(Math.abs(-5));System.out.println(Math.pow(2,5));

}4.00.787215267182144215.1532.0

Examplepublic class Circle{

// Other code goes here

// Returns the circumference of the Circlepublic double findCircumference(){ return Math.PI * diameter; }

// Returns the area of the Circlepublic double findArea(){ double radius = diamter/2; return Math.PI * Math.pow(radius,2);

}

}

Math.random()The method Math.random() is really useful. Recall it returns a double from 0.0 to 1.0 (but not including 1.0)

So values we might get could be:

•.342519638...

•.00043242...

•.956832443...

A clever way to find a random integer between 0 and 5 inclusive we could multiply by 6 and find the integer value of that number.

• int randomFrom0To5= (int)(Math.random()*6);

If we wanted a random value from 1 to 52, we could do much the same, multiply by 52 (this would give us values from 0 to 51.9999. If we took the (int) of that we would get values from 0 to 51. We then would have to add 1 to that.

• int randomFrom1To52= (int)(Math.random()*52) + 1;