PercolationStats

import edu.princeton.cs.algs4.StdRandom;
import edu.princeton.cs.algs4.StdStats;

public class PercolationStats {
    private static final double CONFIDENCE_95 = 1.96;
    private final int times;
    private final double stddev;
    private final double mean;

    public PercolationStats(int n, int times) {
        this.times = times;
        if (n <= 0 || times <= 0)
            throw new IllegalArgumentException("not valid indices");

        double [] thresholds = new double[times];
        // runs times times the monteCarlo simulation
        for (int i = 0; i < times; i++) {
            thresholds[i] = monteCarlo(n);
        }
        mean = StdStats.mean(thresholds);
        stddev = StdStats.stddev(thresholds);
    }

    public double mean() {
        return mean;
    }

    public double stddev() {
        return stddev;
    }

    public double confidenceLo() {
        return (mean - ((CONFIDENCE_95 * stddev) / Math.sqrt(times)));
    }

    public double confidenceHi() {
        return (mean + ((CONFIDENCE_95 * stddev) / Math.sqrt(times)));
    }

    private double monteCarlo(int n) {
        Percolation percolation = new Percolation(n);
        int p;
        int q;
        int opened = 0;
        // as long as the system does not percolate whe open a new random site
        while (!percolation.percolates()) {
            p = StdRandom.uniform(1, n + 1); // a random site index in a n size grid + 1 as last item is excluded
            q = StdRandom.uniform(1, n + 1); // an other random site
            if (!percolation.isOpen(p, q)) {
                percolation.open(p, q);
                opened++;
            }
        }
        return opened * 1.0 / (n * n);
    }

    public static void main(String[] args) {
        int n = Integer.parseInt(args[0]);
        int t = Integer.parseInt(args[1]);
        PercolationStats stats = new PercolationStats(n, t);
        System.out.println("mean                   = " + stats.mean);
        System.out.println("stddev                  = " + stats.stddev);
        System.out.println("95% confidence interval = [" + stats.confidenceLo()
                + ", " + stats.confidenceHi() + " ]");
    }
}