/* * BioJava development code * * This code may be freely distributed and modified under the * terms of the GNU Lesser General Public Licence. This should * be distributed with the code. If you do not have a copy, * see: * * http://www.gnu.org/copyleft/lesser.html * * Copyright for this code is held jointly by the individual * authors. These should be listed in @author doc comments. * * For more information on the BioJava project and its aims, * or to join the biojava-l mailing list, visit the home page * at: * * http://www.biojava.org/ * */ package org.biojava.utils; import java.util.AbstractSet; import java.util.Collection; import java.util.ConcurrentModificationException; import java.util.HashSet; import java.util.Iterator; import java.util.Set; /** * Lightweight implementation of Set which uses little memory to store a small * number of items, at the expense of scalability. Not recomended for more than * 20-30 items. * *
* This implementation has the useful property that the iteration order is the * same as the order in which the items are added. *
* * @author Matthew Pocock */ public class SmallSet extends AbstractSet { private int vid = 0; private Object[] items; private int numItems; public SmallSet() { this(2); } public SmallSet(int size) { items = new Object[size]; numItems = 0; } public SmallSet(Collection col) { if (! (col instanceof Set)) { col = new HashSet(col); } numItems = col.size(); items = new Object[numItems]; items = col.toArray(items); } public boolean contains(Object o) { for(int i = 0; i < numItems; i++) { if(items[i].equals(o)) { return true; } } return false; } public int size() { return numItems; } public boolean add(Object o) { if(this.contains(o)) { return false; } if(numItems == items.length) { Object[] tmp = new Object[items.length * items.length]; System.arraycopy(items, 0, tmp, 0, items.length); this.items = tmp; } this.items[this.numItems++] = o; vid++; return true; } // remove by index private boolean remove(int i) { System.arraycopy(items, i, items, i-1, numItems - i); numItems--; vid++; return true; } public Iterator iterator() { return new Iterator() { int vid = SmallSet.this.vid; int i = 0; public boolean hasNext() { validate(); return i < numItems; } public Object next() { validate(); return items[i++]; } public void remove() { validate(); SmallSet.this.remove(i--); this.vid = SmallSet.this.vid; } private void validate() { if(this.vid != SmallSet.this.vid) { throw new ConcurrentModificationException(); } } }; } }