Android Open Source - flingbox Position Comparator

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License

The source code is released under:

GNU General Public License

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Java Source Code

/*
 *  Flingbox - An OpenSource physics sandbox for Google's Android
 *  Copyright (C) 2009  Jon Ander Pealba & Endika Gutirrez
 */*from w w w . j  a  va  2 s .c  o  m*/
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

package edu.eside.flingbox.utils;

import java.util.Comparator;

import edu.eside.flingbox.math.Vector2D;

/**
 * Abstract class to arrange objects by it's position
 * in the scene.
 */
public class PositionComparator  {
  /**
   * Interface of an object that can be located
   */
  public static interface Positionable {
    Vector2D getPosition();
  }
  
  /**
   * Local class of an generic position comparator
   */
  protected static class ByPositionComparator  implements Comparator<Positionable> {
    public final static int UPPER_SENSE = 1;
    public final static int LOWER_SENSE = 1;
    private final int mSense;
    
    ByPositionComparator(int sense) {
      mSense = sense;
    }
    
    @Override
    public int compare(Positionable pos0, Positionable pos1) {
      if (pos0 == pos1)
        return 0;
      float verticalPos1 = pos0.getPosition().projectOver(mGroundSense);
      float verticalPos2 = pos1.getPosition().projectOver(mGroundSense);
      return verticalPos1 > verticalPos2 ? mSense : -mSense;
    }
    
  }
  
  /** Vector to ground. By default (0, -1) */
  private static Vector2D mGroundSense = new Vector2D(0, -1f);
  
  /** To order from the top of the scene to the bottom */
  public final static ByPositionComparator UPPER_COMPARATOR = new ByPositionComparator(ByPositionComparator.UPPER_SENSE);
  /** To order from the bottom of the scene to the top */
  public final static ByPositionComparator LOWER_COMPARATOR = new ByPositionComparator(ByPositionComparator.LOWER_SENSE);
  
  /**
   * Sets ground vector
   * 
   * @param sense
   */
  public static void setGroundSense(Vector2D sense) {
    mGroundSense = sense;
  }
}

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