Java tutorial
/* * Copyright 2013, 2014 Deutsche Nationalbibliothek * * Licensed under the Apache License, Version 2.0 the "License"; * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.culturegraph.mf.util.tries; import java.util.Collection; import java.util.HashSet; import java.util.Map; import java.util.Set; import org.apache.commons.lang.NotImplementedException; /** * A {@link Map} with char as key. Used for set matching, tries etc. <br> * <strong>Important:</strong> It is optimized for size in memory. No extra information for fast entry/keySet/values iteration etc. is held. * * @author Markus Michael Geipel * * @param <V> */ final class CharMap<V> implements Map<Character, V> { private static final int INITIAL_CAPACITY = 2; private static final float LOAD_FACTOR = 1f; private Entry<V>[] table; private int size; @SuppressWarnings("unchecked") public CharMap() { table = new Entry[INITIAL_CAPACITY]; } @Override public int size() { return size; } @Override public boolean isEmpty() { return size() == 0; } @Override public boolean containsKey(final Object key) { throw new NotImplementedException(); } @Override public boolean containsValue(final Object value) { throw new NotImplementedException(); } @Override public V get(final Object key) { if (key instanceof Character) { final Character beite = (Character) key; return get(beite.charValue()); } return null; } public V get(final char key) { Entry<V> entry = table[key % table.length]; while (entry != null) { if (entry.getKeyChar() == key) { return entry.getValue(); } entry = entry.getNext(); } return null; } @Override public V put(final Character key, final V value) { put(key.charValue(), value); return null; } /** * @param key * @param value * @return the parameter value */ public void put(final char key, final V value) { if (size > LOAD_FACTOR * table.length) { expand(); } put(table, key, value); ++size; } public void put(final Entry<V>[] table, final char key, final V value) { final Entry<V> newEntry = new Entry<V>(key, value); Entry<V> entry = table[key % table.length]; if (entry == null) { table[key % table.length] = newEntry; } else { while (entry.getNext() != null) { if (entry.getKeyChar() == key) { throw new IllegalStateException("Key '" + key + "' already used"); } entry = entry.getNext(); } entry.setNext(newEntry); } } private void expand() { final int newSize = 2 * table.length; @SuppressWarnings("unchecked") final Entry<V>[] newTable = new Entry[newSize]; for (Entry<V> entry : table) { Entry<V> temp = entry; while (temp != null) { put(newTable, temp.getKeyChar(), temp.getValue()); temp = temp.getNext(); } } table = newTable; } @Override public V remove(final Object key) { throw new NotImplementedException(); } @Override public void putAll(final Map<? extends Character, ? extends V> map) { throw new NotImplementedException(); } @Override public void clear() { throw new NotImplementedException(); } @Override public Set<Character> keySet() { final Set<Character> keys = new HashSet<Character>(); for (int i = 0; i < table.length; ++i) { Entry<V> entry = table[i]; while (entry != null) { keys.add(entry.getKey()); entry = entry.getNext(); } } return keys; } @Override public Collection<V> values() { final Set<V> values = new HashSet<V>(); for (int i = 0; i < table.length; ++i) { Entry<V> entry = table[i]; while (entry != null) { values.add(entry.getValue()); entry = entry.getNext(); } } return values; } @Override public Set<java.util.Map.Entry<Character, V>> entrySet() { final Set<java.util.Map.Entry<Character, V>> entries = new HashSet<java.util.Map.Entry<Character, V>>(); for (int i = 0; i < table.length; ++i) { Entry<V> entry = table[i]; while (entry != null) { entries.add(entry); entry = entry.getNext(); } } return entries; } /** * * @param <V> */ private static final class Entry<V> implements Map.Entry<Character, V> { private final char key; private V value; private Entry<V> next; Entry(final char key, final V value) { this.key = key; this.value = value; } public Entry<V> getNext() { return next; } public char getKeyChar() { return key; } public void setNext(final Entry<V> next) { this.next = next; } @Override public Character getKey() { return Character.valueOf(key); } @Override public V getValue() { return value; } @Override public V setValue(final V value) { final V old = this.value; this.value = value; return old; } @Override public String toString() { return key + "=" + value; } } }