Java tutorial
/* * Copyright (c) 2001-2008 Caucho Technology, Inc. All rights reserved. * * The Apache Software License, Version 1.1 * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in * the documentation and/or other materials provided with the * distribution. * * 3. The end-user documentation included with the redistribution, if * any, must include the following acknowlegement: * "This product includes software developed by the * Caucho Technology (http://www.caucho.com/)." * Alternately, this acknowlegement may appear in the software itself, * if and wherever such third-party acknowlegements normally appear. * * 4. The names "Burlap", "Resin", and "Caucho" must not be used to * endorse or promote products derived from this software without prior * written permission. For written permission, please contact * info@caucho.com. * * 5. Products derived from this software may not be called "Resin" * nor may "Resin" appear in their names without prior written * permission of Caucho Technology. * * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE * DISCLAIMED. IN NO EVENT SHALL CAUCHO TECHNOLOGY OR ITS CONTRIBUTORS * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, * OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN * IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. * * @author Scott Ferguson */ /** * The IntMap provides a simple hashmap from keys to integers. The API is * an abbreviation of the HashMap collection API. * * The convenience of IntMap is avoiding all the silly wrapping of * integers. */ public class IntMap { /** * Encoding of a null entry. Since NULL is equal to Integer.MIN_VALUE, * it's impossible to distinguish between the two. */ public final static int NULL = 0xdeadbeef; // Integer.MIN_VALUE + 1; private static final Object DELETED = new Object(); private Object[] _keys; private int[] _values; private int _size; private int _mask; /** * Create a new IntMap. Default size is 16. */ public IntMap() { _keys = new Object[256]; _values = new int[256]; _mask = _keys.length - 1; _size = 0; } /** * Clear the hashmap. */ public void clear() { Object[] keys = _keys; int[] values = _values; for (int i = keys.length - 1; i >= 0; i--) { keys[i] = null; values[i] = 0; } _size = 0; } /** * Returns the current number of entries in the map. */ public int size() { return _size; } /** * Puts a new value in the property table with the appropriate flags */ public int get(Object key) { int mask = _mask; int hash = key.hashCode() % mask & mask; Object[] keys = _keys; while (true) { Object mapKey = keys[hash]; if (mapKey == null) return NULL; else if (mapKey == key || mapKey.equals(key)) return _values[hash]; hash = (hash + 1) % mask; } } /** * Expands the property table */ private void resize(int newSize) { Object[] newKeys = new Object[newSize]; int[] newValues = new int[newSize]; int mask = _mask = newKeys.length - 1; Object[] keys = _keys; int values[] = _values; for (int i = keys.length - 1; i >= 0; i--) { Object key = keys[i]; if (key == null || key == DELETED) continue; int hash = key.hashCode() % mask & mask; while (true) { if (newKeys[hash] == null) { newKeys[hash] = key; newValues[hash] = values[i]; break; } hash = (hash + 1) % mask; } } _keys = newKeys; _values = newValues; } /** * Puts a new value in the property table with the appropriate flags */ public int put(Object key, int value) { int mask = _mask; int hash = key.hashCode() % mask & mask; Object[] keys = _keys; while (true) { Object testKey = keys[hash]; if (testKey == null || testKey == DELETED) { keys[hash] = key; _values[hash] = value; _size++; if (keys.length <= 4 * _size) resize(4 * keys.length); return NULL; } else if (key != testKey && !key.equals(testKey)) { hash = (hash + 1) % mask; continue; } else { int old = _values[hash]; _values[hash] = value; return old; } } } /** * Deletes the entry. Returns true if successful. */ public int remove(Object key) { int mask = _mask; int hash = key.hashCode() % mask & mask; while (true) { Object mapKey = _keys[hash]; if (mapKey == null) return NULL; else if (mapKey == key) { _keys[hash] = DELETED; _size--; return _values[hash]; } hash = (hash + 1) % mask; } } public String toString() { StringBuffer sbuf = new StringBuffer(); sbuf.append("IntMap["); boolean isFirst = true; for (int i = 0; i <= _mask; i++) { if (_keys[i] != null && _keys[i] != DELETED) { if (!isFirst) sbuf.append(", "); isFirst = false; sbuf.append(_keys[i]); sbuf.append(":"); sbuf.append(_values[i]); } } sbuf.append("]"); return sbuf.toString(); } }