import java.util.Scanner;

public class Logarithm {

public static void main(String[] args) {

System.out.println("printLogarithm");

printLogarithm(3.0);

Scanner in = new Scanner(System.in);

System.out.println("scandouble");

scanDouble(in);

System.out.println("scandouble2");

scanDouble2(in);

}

public static void printLogarithm(double x) {

if (x <= 0.0) {

System.err.println("Error: x must be positive.");

return;

}

double result = Math.log(x);

System.out.println("The log of x is " + result);

}

public static void scanDouble(Scanner in) {

System.out.print("Enter a number: ");

double x = in.nextDouble();

printLogarithm(x);

}

public static void scanDouble2(Scanner in) {

System.out.print("Enter a number: ");

if (!in.hasNextDouble()) {

String word = in.next();

System.err.println(word + " is not a number");

return;

}

double x = in.nextDouble();

printLogarithm(x);

}

}