Benchmark that measures alternative implementations of a map with case-insensitive string keys. The first implementation is a hash-map whose keys are converted to upper-case. The second implementation is a list whose entries are compared using String.equalsIgnoreCase. The two interesting variables are n (the number of elements in the collection)…

CaseInsensitiveMapVersusListBenchmark.java

/**
 * Benchmark that measures alternative implementations of a map with case-insensitive
 * string keys. The first implementation is a hash-map whose keys are converted to
 * upper-case. The second implementation is a list whose entries are compared using
 * String.equalsIgnoreCase.
 *
 * <p>The two interesting variables are n (the number of elements in the collection)
 * and name(int x) (the function that generates the list of entries).
 *
 * <p>We access each element of the collection once, because that will be typical for
 * my motivating use case, ResultSet.getString(String).
 *
 * <p>List seems to be the faster implementation up to about n = 35.
 */
public class CaseInsensitiveMapVersusListBenchmark {
  public static void main(String[] args) {
    final HashMap<String, Integer> map = new HashMap<String, Integer>();
    final List<String> list = new ArrayList<String>();
    int n = 40;
    for (int i = 0; i < n; i++) {
      String s = name(i);
      map.put(s.toUpperCase(), i);
      list.add(s);
    }
    for (int z = 0; z < 3; z++) {
      long t0 = System.nanoTime();
      int k = xxxx(map, n);
      System.out.println("map:  " + (System.nanoTime() - t0) + " : " + k);
      t0 = System.nanoTime();
      xxxx(list, n);
      System.out.println("list: " + (System.nanoTime() - t0) + " : " + k);
    }

  }

  static String name(int i) {
    return "xxxxxxx" + i;
  }

  static int xxxx(List<String> list, int n) {
    int x = 0;
    for (int i = 0; i < n; i++) {
      final String s = name(i);
      x += anInt(list, s);
    }
    return x;
  }

  static int anInt(List<String> list, String s) {
    final int size = list.size();
    for (int i = 0; i < size; i++) {
      String s1 = list.get(i);
      if (s1.equalsIgnoreCase(s)) {
        return i;
      }
    }
    return -1;
  }

  static int xxxx(HashMap<String, Integer> map, int n) {
    int x = 0;
    for (int i = 0; i < n; i++) {
      x += map.get((name(i)).toUpperCase());
    }
    return x;
  }
}