PercolationStats.java

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

public class PercolationStats {

    private final int trials;
    private final double[] fractions;

    public PercolationStats(int n, int t) {
        if (n <= 0 || t <= 0) {
            throw new IllegalArgumentException("Given n <= 0 || t <= 0");
        }

        this.trials = t;
        this.fractions = new double[t];

        for (int i = 0; i < this.trials; i++) {
            Percolation percolation = new Percolation(n);

            int result = 0;
            while (!percolation.percolates()) {
                int row = StdRandom.uniform(1, n + 1);
                int col = StdRandom.uniform(1, n + 1);

                if (!percolation.isOpen(row, col)) {
                    percolation.open(row, col);
                    result++;
                }

            }
            double fraction = (double) result / (double) (n * n);
            fractions[i] = fraction;
        }
    }

    public static void main(String[] args) {
        int n = Integer.parseInt(args[0]);
        int t = Integer.parseInt(args[1]);
        PercolationStats ps = new PercolationStats(n, t);

        String confidence = ps.confidenceLo() + ", " + ps.confidenceHi();
        StdOut.println("mean                    = " + ps.mean());
        StdOut.println("stddev                  = " + ps.stddev());
        StdOut.println("95% confidence interval = " + confidence);
    }

    public double mean() {
        return StdStats.mean(fractions);
    }

    public double stddev() {
        return StdStats.stddev(fractions);
    }

    public double confidenceLo() {
        return mean() - (1.96 * stddev() / Math.sqrt(trials));
    }

    public double confidenceHi() {
        return mean() + ((1.96 * stddev()) / Math.sqrt(trials));
    }

}