Java's Math class  

  • Recall:

    • A class in Java contains variables and methods:

    • A method contains statements that performs an important task

  • Java provides many Mathematical methods stored in a class called Math

Java's Math class

  • Some of the Math methods defined in the Math class of Java's library: 

     public class Math
 {
    public static double sin(double x) { ... }
    public static double cos(double x) { ... }
    public static double tan(double x) { ... }

    public static double exp(double x) { ... }            // ex
    public static double log(double x) { ... }		  // Natural log
    public static double log10(double x) { ... }
    public static double pow(double a, double b) { ... }  // ab
    public static double sqrt(double x) { ... }           // √x

    public static double random( ) { ... }

    public static double max(double a, double b) { ... }
    public static double min(double a, double b) { ... }
    public static double abs(double x) { ... }           // absolute value  
 }

How to use a method in Java's Math class

  • How to invoke a method in Java's Math class: 

       Math.methodName( ... )

    Example:   compute (1) the square root of 49 and (2) 23: 

    public class MathMethods
{
   public static void main(String[] args) 
   {
       double x;
       
       x = Math.sqrt(49);
       x = Math.pow(2, 3);
   }
}

DEMO: demo/04-Math+String/01-Math-class/MathMethods.java

Compute the distance between 2 points

  • The mathematical formula to compute the distance between a point (x1, y1) and another point (x2, y2) is: 

      distance = √(x2 - x1)2 + (y2 - y1)2 

  • We will use this formula to write a program to compute the distance between 2 points next

Compute the distance between 2 points

  • Java program that computes the distance between 2 points: 

    import java.util.Scanner;

public class Distance
{
   public static void main(String[] args) 
   {
       Scanner input = new Scanner(System.in);
       double x1, y1, x2, y2, distance;
       
       // Read in the coordinates (x1,y1) and (x2,y2)
       x1 = input.nextDouble();
       y1 = input.nextDouble();
       x2 = input.nextDouble();
       y2 = input.nextDouble();
       
       distance = Math.sqrt( Math.pow((x1-x2), 2)
                           + Math.pow((y1-y2), 2) );
   }
}

DEMO: demo/04-Math+String/01-Math-class/Distance.java