Java Stats类详解

[Stats]
- data: double[]
--
+ Stats(data: double[])
+ sum(): double
+ mean(): double
+ median(): double
+ stddev(): double

public class Stats {

    private double[] data;

    public Stats(double[] data) {
        this.data = data;
    }

    public double sum() {
        double sum = 0;
        for (double num : data) {
            sum += num;
        }
        return sum;
    }

    public double mean() {
        return sum() / data.length;
    }

    public double median() {
        Arrays.sort(data);
        if (data.length % 2 == 0) {
            return (data[data.length / 2 - 1] + data[data.length / 2]) / 2.0;
        } else {
            return data[data.length / 2];
        }
    }

    public double stddev() {
        double mean = mean();
        double sum = 0;
        for (double num : data) {
            sum += Math.pow(num - mean, 2);
        }
        return Math.sqrt(sum / data.length);
    }

    public static void main(String[] args) {
        double[] data = {1, 2, 3, 4, 5};
        Stats stats = new Stats(data);

        System.out.println("Sum: " + stats.sum());
        System.out.println("Mean: " + stats.mean());
        System.out.println("Median: " + stats.median());
        System.out.println("Standard Deviation: " + stats.stddev());
    }
}

Sum: 15.0
Mean: 3.0
Median: 3.0
Standard Deviation: 1.4142135623730951