[Ch4] Renamed variables in Mixed messages exercise to be more consistent with modern Java

  public static void main(String[] args) {

    int count = 0;

    Mix4[] m4a = new Mix4[20];

    int x = 0;

    Mix4[] mixes = new Mix4[20];

    int i = 0;

//    while () {

      m4a[x] = new Mix4();

      m4a[x].counter = m4a[x].counter + 1;

      mixes[i] = new Mix4();

      mixes[i].counter = mixes[i].counter + 1;

      count = count + 1;

      count = count + m4a[x].maybeNew(x);

      x = x + 1;

      count = count + mixes[i].maybeNew(i);

      i = i + 1;

//    }

    System.out.println(count + " "

                       + m4a[1].counter);

    System.out.println(count + " " +

                       mixes[1].counter);

  }

  public int maybeNew(int index) {

//    if (             ) {

      Mix4 m4 = new Mix4();

      m4.counter = m4.counter + 1;

      Mix4 mix = new Mix4();

      mix.counter = mix.counter + 1;

      return 1;

//    }

//    return 0;