// Example 21 from page 17 of Java Precisely second edition (The MIT Press 2005)
// Author: Peter Sestoft (sestoft@itu.dk)

import java.util.Random;

class Example21 {
  public static void main(String[] args) {
    if (args.length != 1) 
      System.out.println("Usage: java Example21 <length>\n");
    else {
      System.out.println("Timing character replacement in a string:");
      Random rnd = new Random();
      int length = Integer.parseInt(args[0]);
      char[] cbuf = new char[length];
      for (int i=0; i<length; i++) 
        cbuf[i] = (char)(65 + rnd.nextInt(26));
      String s = new String(cbuf);
      for (int i=0; i<10; i++) {
        Timer t = new Timer();
        String res = replaceCharChar(s, 'A', 'H');
        System.out.print(t.check() + " ");
      }
      System.out.println();
    } 
  }
  
  static String replaceCharChar(String s, char c1, char c2) {
    char[] res = new char[s.length()];
    for (int i=0; i<s.length(); i++) 
      if (s.charAt(i) == c1) 
        res[i] = c2;
      else
        res[i] = s.charAt(i);
    return new String(res);
  }

  private final static class Timer {
    private long starttime;
    
    public Timer() { starttime = System.currentTimeMillis(); }
    
    double check() {
      return (System.currentTimeMillis()-starttime)/1000.0;
    }
  }
}