A sortable, ordered Map

janhoo (Jan Galinski) — Thu, 21 Sep 2006 20:01:44 GMT

This is a neat collection that allows its elements to be sorted arbitary by moving them up and down in the List or put them to a given index. Nice to display lists that can be edited (i.e. reordered) by the user.



import java.util.ArrayList;

import java.util.Collection;

import java.util.Iterator;

import java.util.List;



import org.apache.commons.collections.map.ListOrderedMap;



/**

 * @author janhoo

 */

public class SortableOrderedMap extends ListOrderedMap {



  /**

   * Inserts a given Key/Value-Pair on a certain Position

   * alle following Pairs are moved up accordingly 

   * 

   * @param newKey

   * @param newValue

   * @param pos

   * @return

   */

  public Object putOnPosition(Object newKey, Object newValue, int pos) {

    Object res = put(newKey, newValue);

    while (indexOf(newKey) > pos) {

      moveUp(newKey);

    }

    return res;

  }



  /**

   * Inserts a given Key/Value Pair before position of a given Key

   * 

   * @param newKey

   * @param newValue

   * @param oldKey

   * @return

   */

  public Object putBefore(Object newKey, Object newValue, Object oldKey) {

    if (!containsKey(oldKey)) {

      return put(newKey, newValue);

    }

    return putOnPosition(newKey, newValue, indexOf(oldKey));

  }



  /**

   * 

   * inserts a given key/value pair after the position of a given key

   * 

   * @param newKey

   * @param newValue

   * @param oldKey

   * @return

   */

  public Object putAfter(Object newKey, Object newValue, Object oldKey) {

    if (!containsKey(oldKey)) {

      return put(newKey, newValue);

    }

    return putOnPosition(newKey, newValue, indexOf(oldKey)+1);

  }

	

  /**

   * moves item with given key up by one step. Does nothing

   * if the item is already on top or not existend.

   * 

   * @param the key of the Item to be moved

   */

  public synchronized void moveUp(Object key) {



    // return if already on top or key not in map	

    if (key.equals(firstKey()) || !containsKey(key)) {

      return;

    }

    int pcur = indexOf(key);



    insertOrder.set(pcur, previousKey(key));

    insertOrder.set(pcur - 1, key);

  }



  /**

   * moves item with given key down by one step. Does nothing

   * if the item is already on bottom or not existend.

   * 

   * @param the key of the Item to be moved

   */

  public synchronized void moveDown(Object key) {

    if (key.equals(lastKey()) || !containsKey(key)) {

      return;

    }

    int pcur = indexOf(key);

    insertOrder.set(pcur, nextKey(key));

    insertOrder.set(pcur + 1, key);

  }



  /* (non-Javadoc)

   * @see org.apache.commons.collections.map.ListOrderedMap#asList()

   */

  public List asList() {

    ArrayList v = new ArrayList();

    for (Iterator it = values().iterator(); it.hasNext();) {

      v.add(it.next());

    }

    return v;

  }



	

  /* (non-Javadoc)

   * @see java.lang.Object#toString()

   */

  public String toString() {

    StringBuffer b = new StringBuffer();

    for (Iterator it = values().iterator(); it.hasNext();) {

      b.append(it.next().toString() + "\n");

    }  

    return b.toString();

  }

}

Attention: this requires the jakarta commons collections

DZone Snippets: sortable code

A sortable, ordered Map