Android Open Source - TaskButler Task Auto Comparator

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License

The source code is released under:
GNU General Public License
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Java Source Code

/*
 * TaskAutoComparator.java// w ww .  j  av a 2  s  .  co m
 * 
 * Copyright 2012 Jonathan Hasenzahl, James Celona, Dhimitraq Jorgji
 * 
 * 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.worcester.cs499summer2012.comparator;

import java.util.Comparator;

import edu.worcester.cs499summer2012.task.Task;

/**
 * Comparator for auto-sorting tasks.
 * @author Jonathan Hasenzahl
 */
public class TaskAutoComparator implements Comparator<Task> {

  /**
   * This comparator will sort a task by the following method:
   *     1. Compare by completion status. An uncompleted task is ranked 
   *        before a completed task. If completion statuses are the same:
   *     2. Compare by due date. A task with an earlier due date 
   *        is ranked before a task with a later due date. A task with a due
   *        date is ranked before a task without a due date. If due dates are
   *        the same:
   *     3. Compare by priority. Urgent tasks are ranked before normal tasks 
   *        which are ranked before trivial tasks. If priorities are the
   *        same:
   *     4. Compare by creation date. Tasks with an earlier creation date are
   *        ranked before tasks with a later creation date.
   * @param lhs the first task
   * @param rhs the second task
   * @return A negative value if the first task if the first task is ordered 
   *         before the second task, 0 if they are ordered the same, or a 
   *         positive value if the second task is ordered before the first 
   *         task
   */
  public int compare(Task lhs, Task rhs) {
    // Step 1: Compare by completion status
    if (!lhs.isCompleted() && rhs.isCompleted())
      return -1;
    if (lhs.isCompleted() && !rhs.isCompleted())
      return 1;
    
    // Step 2: Compare by due date
    if (!lhs.hasDateDue()) {
      // Case 1: lhs has no due date
      if (rhs.hasDateDue()) {
        // Case 1a: rhs has a due date and is ordered first
        return 1;
      }
    }
    else {
      // Case 2: lhs has a due date
      if (!rhs.hasDateDue()) {
        // Case 2a: rhs has no due date and is ordered second
        return -1;
      }
      else {
        // Case 2b: rhs has a due date and the due dates must be
        // checked for equality
        if (lhs.getDateDue() != rhs.getDateDue()) {
          // Due dates are not equal, now we can compare them
          // Ex. LHS -> date 5000ms (earlier)
          //     RHS -> date 6000ms (later)
          //     LHS - RHS = 5000 - 6000 = -1000 = LHS ordered first
          long diff = lhs.getDateDue() - rhs.getDateDue();
          
          return diff < 0 ? -1 : 1;
        }
      }
    }
    
    // Step 3: Compare by priority
    // Ex: LHS -> priority 2 (urgent)
    //     RHS -> priority 1 (normal)
    //     RHS - LHS = 1 - 2 = -1 = LHS ordered first
    if (lhs.getPriority() != rhs.getPriority())
      return rhs.getPriority() - lhs.getPriority();    
    
    // Step 4: Compare by creation date
    // Ex. LHS -> date 5000ms (earlier)
    //     RHS -> date 6000ms (later)
    //     LHS - RHS = 5000 - 6000 = -1000 = RHS ordered first
    long diff = lhs.getDateCreated() - rhs.getDateCreated();
    
    if (diff < 0)
      return 1;
    
    if (diff > 0)
      return -1;
    
    return 0;
  }

}
Java Source Code List
