Math ClassMath Class

AP CS 2012AP CS 2012

Mathfrequently used methods

Name Usefloor() rounds down

ceil() rounds up

pow(x,y) returns x to the power of y

abs() returns the absolute value

sqrt() returns the square root

round() rounds the nearest whole number

max(x,y) returns bigger of x and y

min(x,y) returns smaller of x and y

random() returns a double in the range [0, 1.0)

All methods in the Math class are static.All methods in the Math class are static. Static methods do not require the creation of Static methods do not require the creation of

an object to invoke them (use them).an object to invoke them (use them). Static methods are invoked through the class Static methods are invoked through the class

name.name. When we have methods that will give the When we have methods that will give the

same result regardless of the object, we use same result regardless of the object, we use static methods. We would want sqrt() method static methods. We would want sqrt() method to compute the square root of the number the to compute the square root of the number the same every time, regardless of the individual same every time, regardless of the individual object that may be created. object that may be created.

Math.floor(3.254) Math.ceil(2.45)Math.pow(2,7) Math.abs(-9)Math.sqrt(256)Math.round(3.6)Math.max(5,7)

Most Math methods return a double, but some do return integer values.We use the class name, Math, to call these methods, becausethey are static.

= 3.0= 3.0= 128.0= 9.0= 16= 4.0= 7

//math return methods

import java.lang.*;

public class MathMethods{ public static void main ( String[] args ) { System.out.println(Math.floor(3.254)); //= 3.0 System.out.println(Math.ceil(2.45)); //= 3.0 System.out.println(Math.pow(2,7)); //= 128.0 System.out.println(Math.abs(-9)); //= 9 System.out.println(Math.sqrt(256)); //= 16.0 System.out.println(Math.sqrt(144)); //= 12.0

System.out.println(Math.round(3.6)); //= 4 System.out.println(Math.max(5,7)); //= 7 System.out.println(Math.max(5,-7)); //= 5 System.out.println(Math.min(5,7)); //= 5 System.out.println(Math.min(5,-7)); //= -7 }}

Type this intoDr. Java and runit. Change the numbers and seehow it changesyour output.

Some of the programming that is done in the real world is with games. Games must havethe ability to vary or be random; thus,you must have the ability to generaterandom numbers.

Math.random(); // returns a random number//between 0 up to, but not//including 1.

public class RandomDemo{

public static void main ( String[] args ){ double dblans; int intans; dblans = Math.random() * 10; intans = (int)(Math.random() * 10); //this line needs help

System.out.println("\nMath.random()"); System.out.println( dblans ); System.out.println( intans ); //why does it always output 0?

}} Math.random() * 10;

returns a double between 0 and 9.999999

(int) Math.random() * 10;When we typecast a double as an int,

we get a number between 0 and 9 inclusively

public class RandomDemo{

public static void main ( String[] args ){

double dblans;int intans;dblans = Math.random() * 10;intans = (int)(Math.random() * 10);

System.out.println("\nMath.random()");System.out.println( dblans );System.out.println( intans );

}}

How does the addition of parenthesis changethis program?

Random NumbersRandom Numbers

How can you use Math.random() to How can you use Math.random() to simulate rolling a die? How can we simulate rolling a die? How can we get it to return the numbers 1 – 6?get it to return the numbers 1 – 6?

(int)(Math.random()*6) + 1;(int)(Math.random()*6) + 1;