Compare two sorting algorithms(P256)

//比较排序算法速度

import edu.princeton.cs.algs4.*;

public class SortCompare
{
    public static double time(String alg, Double[] a)
    {
        Stopwatch timer = new Stopwatch();
        if(alg.equals("Insertion")) Insertion.sort(a);
        if(alg.equals("Selection")) Selection.sort(a);
        if(alg.equals("Shell")) Shell.sort(a);
        if(alg.equals("Quick")) Quick.sort(a);
        if(alg.equals("Heap")) Heap.sort(a);
        return timer.elapsedTime();
    }
    
    public static double timeRandomInput(String alg, int N, int T)//T次，每次N个
    {
        double total = 0.0;
        Double[] a = new Double[N];
        for(int t = 0; t < T; t++)
        {
            for(int i = 0; i < N; i++)
                a[i] = StdRandom.uniform();
            total += time(alg,a);
        }
        return total;
    }
    
    public static void main(String[] args)
    {
        String alg1 = args[0];
        String alg2 = args[1];
        int N = Integer.parseInt(args[2]);
        int T = Integer.parseInt(args[3]);
        double t1 = timeRandomInput(alg1, N, T);
        double t2 = timeRandomInput(alg2, N, T);
        StdOut.printf("for %d random doubles\n%s is", N, alg1);
        StdOut.printf(" %.1f times faster than %s\n", t2/t1, alg2);
    }
}