boidsutils.java

自己做的几个j2me程序例子。。只要在Jbuilder里open project就行。。大家看看很有代表性

package example.boids;

import java.util.Random;

class BoidsUtils {
  private static Random random = new Random();

  private BoidsUtils() {

  }

  static int random(int scale) {
    int randomInt = random.nextInt();
    // extend to long, but remove sign-extend
    long randomIntAsLong = (long) randomInt & 0xFFFFFFFFL;
    int result = (int) ( (randomIntAsLong * (long) scale) >> 32);
    return result;
  }

    // This seems to produce the square root rounded down to the next
    // integer, except for numbers very near the next square, when we
    // get the square root rounded up to the next integer. That's good
    // enough for our purposes here anyway. In use in the boids MIDlet,
    // it averages about 14 iterations per use.
  static int squareRoot(int square) {
    int guess = square;
    if (square < 0) {
      throw new IllegalArgumentException(
          "Negative argument to squareRoot");
    }
    else if (square != 0) {
      int oldGuess;
      do {
        // Newton's method
        oldGuess = guess;
        guess = (oldGuess + square / oldGuess) >> 1;
      }
      while ( (guess < oldGuess) && (guess > 0));
    }

    return guess;
  }
}