Solution to problem 7.12

The easy solution if we do not have to worry about creating a RootApproximator class:

public class Main {
	public static void main(String[] args) {
		System.out.println("Heron's method: successive approximations");
		System.out.println(heron(101));
		System.out.println("Math.sqrt");
		System.out.println(Math.sqrt(101));
	}
	
	public static double heron(double n) {
		double guess = 1;
		while (!closeEnough(guess, n)) {
			guess = (guess + (n/guess)) / 2;
			System.out.println(guess);
		} 
		return guess;
	}
	
	public static boolean closeEnough(double guess, double n) {
		final double THRESHOLD = .000000001;
		return (Math.abs(guess * guess - n)) < THRESHOLD;
	}
}

The more complicated way if we need RootApproximator.java (note that the while loop is in main():

public class RootApproximator {
	private double answer;
	private double guess;
	private final double TOLERANCE = .000000001;
	
	public RootApproximator(double n) {
		answer = n;
		guess = 1;
	}
	
	public boolean isNotCloseEnough() {
		return Math.abs(guess*guess - answer) > TOLERANCE;
	}
	
	public double nextGuess() {
		guess = (guess + (answer/guess)) / 2;
		return guess;
	}
	
	public double firstGuess() {
		return guess;
	}
}

In Main.java:

public class Main {
	public static void main(String[] args) {
		RootApproximator r = new RootApproximator(20);
		System.out.println(r.firstGuess());
		// Using isNotCloseEnough instead of hasGuesses for readability
		while (r.isNotCloseEnough()) {
			System.out.println(r.nextGuess());
		}
	}
}