HashSet and TreeSet performance test

Question

I read about how TreeSet is slower than HashSet, (that adding elements into a TreeSet is slower) so i made a performance test, i\'m trying to find out if it\'s better to add

Answer 1

Try to run this code. I took it from codeforces.ru. This is the demonstration of how HashSet/HashMap may work. It took 1.3 - 1.4 sec to add 10^5 values. According to linked topic - shuffling won't help (I didn't tried). TreeSet will never show such terrible perfomance.

import java.io.*;
import java.util.*;
import static java.lang.Math.*;

public class Main implements Runnable {

    public static void main(String[] args) {
        new Thread(null, new Main(), "", 16 * (1L << 20)).start();
    }

    public void run() {
        try {
            long t1 = System.currentTimeMillis();
            solve();
            long t2 = System.currentTimeMillis();
            System.out.println("Time = " + (t2 - t1));
        } catch (Throwable t) {
            t.printStackTrace(System.err);
            System.exit(-1);
        }
    }

    // solution

    int hashinv(int h) {
        h ^= (h >>> 4) ^ (h >>> 7) ^ (h >>> 8) ^ (h >>> 14) ^ (h >>> 15)
                ^ (h >>> 18) ^ (h >>> 19) ^ (h >>> 20) ^ (h >>> 21)
                ^ (h >>> 23) ^ (h >>> 26) ^ (h >>> 28);
        return h;
    }

    int bitreverse(int h) {
        int res = 0;
        for (int i = 0; i < 31; i++)
            if ((h & (1 << i)) != 0)
                res |= (1 << (30 - i));
        return res;
    }

    void solve() throws IOException {
        final int size = 100000;
        int[] s = new int[size];
        for (int i = 0, val = 0; i < size; i++) {
            s[i] = Integer.MAX_VALUE;
            while (s[i] > 1000000000)
                s[i] = hashinv(bitreverse(val++));
        }
        long startTime = System.currentTimeMillis();
        HashSet h = new HashSet(size);
        for (int i = 0; i < size; i++)
                h.add(s[i]);
        System.out.println("HashSet adding time = " + (System.currentTimeMillis() - startTime));
    }

}