Here is how you use the Math class constant:
double pi = Math.PI;
How much does your result change?
public class CircleArea {
//A Java program to compute the area of a circle
// whose radius is 5
public static void main( String[] args ) {
double r = 5.;
System.out.print ( "Using pi = 3.14: " );
System.out.println( "Area when r = 5: " + 3.14*r*r );
System.out.print ( "Using Math.PI: " );
System.out.println( "Area when r = 5: " + Math.PI*r*r );
}
}
Using pi = 3.14: Area when r = 5: 78.5
Using Math.PI: Area when r = 5: 78.53981633974483
5.3 Write a Java program that prompts the user for a number, and then tells the user whether the number is an
even multiple of 5. Use Scanner to read the number from the user, and use the modulo operator (%)
to decide whether the number is a multiple of 5.
import java.util.Scanner;
public class Mod5 {
//A Java program to detect a multiple of 5
public static void main( String[] args ) {
Scanner sc = new Scanner(System.in);
System.out.print( "Enter an integer: " );
int number = sc.nextInt();
ANSWERS TO REVIEW QUESTIONS 191
if( number % 5 == 0 ) {
System.out.println( number + " is a multiple of 5." );
}
else {
System.out.println( number + " is not a multiple of 5.
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