List containing other lists : Your LinkedList « Collections « Java Tutorial

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/*
 * $Id: ListOfLists.java,v 1.1.1.1 2005/04/07 18:36:24 pocho Exp $
 */


import java.util.AbstractList;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;

/**
 * Creates list containing other lists, access another list's elements as it would belong
 * to this list. 
 * 
 * @version $Name:  $ - $Revision: 1.1.1.1 $ - $Date: 2005/04/07 18:36:24 $
 * TODO Test
 */
public class ListOfLists extends AbstractList {
  private Collection lists = new ArrayList();

  public ListOfLists(Collection c) {
    Iterator it = c.iterator();
    Object o;
    while (it.hasNext()) {
      o = it.next();
      if (o instanceof List)
        lists.add(o);
      else if (o != null)
        throw new UnsupportedOperationException(this.getClass().getName() +
                                                " class supports only instances "+
                                                "of java.util.List interface");
    }
  }

  public int size() {
    Iterator it = lists.iterator();
    int size = 0;
    Object o;
    while (it.hasNext()) {
      o = it.next();
      if (o != null)
        size += ((List) o).size();
    }
    return size;
  }

  public Object get(int index) {
    int size = size();
    if (index < 0)
      throw new IndexOutOfBoundsException("index: " + index +"; size: " + size);

    Iterator it = lists.iterator();
    while (it.hasNext()) {
      List list = (List) it.next();
      if (index < list.size()) {
        return list.get(index);
      }
      else
        index -= list.size();
    }

    // if value has not been returned yet - IndexOutOfBoundsException is thrown
    throw new IndexOutOfBoundsException("index: " + index +"; size: " + size);
  }

  /**
   * Replaces the element at the specified position in underlying list with the
   * specified element.
   *
   * @param index index of element to replace.
   * @param element element to be stored at the specified position.
   * @return the element previously at the specified position.
   */
  public Object set(int index, Object element) {
    int size = size();
    if (index < 0)
      throw new IndexOutOfBoundsException("index: " + index +"; size: " + size);

    Iterator it = lists.iterator();
    while (it.hasNext()) {
      List list = (List) it.next();
      if (index < list.size()) {
        return list.set(index, element);
      }
      else
        index -= list.size();
    }

    // if value has not been returned yet - IndexOutOfBoundsException is thrown
    throw new IndexOutOfBoundsException("index: " + index +"; size: " + size);
  }

  public int indexOf(Object o) {
    ListIterator e = listIterator();
    if (o==null) {
      while (e.hasNext()) {
        if (e.next() == null)
          return e.previousIndex();
      }
    }
    else {
      Object el;
      while (e.hasNext()) {
        el = e.next();
        if (el.equals(o))
          return e.previousIndex();
      }
    }
    return -1;
  }

  public int lastIndexOf(Object o) {
    ListIterator e = listIterator(size());
    if (o==null) {
      while (e.hasPrevious()) {
        if (e.previous() == null)
          return e.nextIndex();
      }
    } else {
      Object el;
      while (e.hasPrevious()) {
        el = e.previous();
        if (el != null && el.equals(o))
          return e.nextIndex();
      }
    }
    return -1;
  }
}