codewarsXXX: Rainfall

Source

//https://www.codewars.com/kata/rainfall/train/java
package codewars.dec;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Rainfall {

	private static double[] array(String town, String str) {
		String part = null;
		int start = str.indexOf(town);
		if (start == -1.0) {
			return new double[0];
		}
		int end = str.indexOf("\n", start);
		if (end == -1) {
			part = str.substring(start);
		} else {
			part = str.substring(start, end);
		}

		String regex = "\\d+\\.\\d";
		double[] arr = new double[12];
		Pattern p = Pattern.compile(regex);
		Matcher m = p.matcher(part);
		int i = 0;
		while (m.find()) {
			arr[i++] = Double.valueOf(m.group());
		}
		return arr;
	}

	public static double mean(String town, String str) {

		double[] arr = Rainfall.array(town, str);
		if (arr.length == 0) {
			return -1.0;
		}
		double sum = 0.0;
		for (double x : arr) {
			sum += x;
		}

		return sum / 12;
	}

	public static double variance(String town, String str) {
		double[] arr = Rainfall.array(town, str);
		if (arr.length == 0) {
			return -1;
		}
		double mean = Rainfall.mean(town, str);
		double sum = 0;
		for (double x : arr) {
			sum += Math.pow(x - mean, 2);
		}
		return sum / 12;
	}
}