From 165e5c3a780a7a1616d3231c3cdfb3590999cd46 Mon Sep 17 00:00:00 2001
From: =?utf8?q?David=20=E2=80=98Bombe=E2=80=99=20Roden?=
 <bombe@freenetproject.org>
Date: Sun, 17 May 2009 22:02:52 +0200
Subject: [PATCH] Add some common collection filters.

---
 src/net/pterodactylus/util/filter/Filters.java | 191 +++++++++++++++++++++++++
 1 file changed, 191 insertions(+)
 create mode 100644 src/net/pterodactylus/util/filter/Filters.java

diff --git a/src/net/pterodactylus/util/filter/Filters.java b/src/net/pterodactylus/util/filter/Filters.java
new file mode 100644
index 0000000..fe3f12f
--- /dev/null
+++ b/src/net/pterodactylus/util/filter/Filters.java
@@ -0,0 +1,191 @@
+/*
+ * jFCPlib - Filters.java -
+ * Copyright © 2009 David Roden
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ */
+package net.pterodactylus.util.filter;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.NoSuchElementException;
+import java.util.Set;
+import java.util.Map.Entry;
+
+/**
+ * Defines various methods to filter {@link Collection}s.
+ *
+ * @author David ‘Bombe’ Roden &lt;bombe@freenetproject.org&gt;
+ */
+public class Filters {
+
+	/**
+	 * Returns a list that contains only the elements from the given list that
+	 * match the given filter.
+	 *
+	 * @param <E>
+	 *            The type of the list elements
+	 * @param list
+	 *            The list to filter
+	 * @param listFilter
+	 *            The list filter
+	 * @return The filtered list
+	 */
+	public static <E> List<E> filteredList(List<E> list, Filter<E> listFilter) {
+		List<E> filteredList = new ArrayList<E>();
+		for (E element : list) {
+			if (listFilter.filterObject(element)) {
+				filteredList.add(element);
+			}
+		}
+		return filteredList;
+	}
+
+	/**
+	 * Returns a set that contains only the elements from the given set that
+	 * match the given filter.
+	 *
+	 * @param <E>
+	 *            The type of the set elements
+	 * @param set
+	 *            The set to filter
+	 * @param setFilter
+	 *            The set filter
+	 * @return The filtered set
+	 */
+	public static <E> Set<E> filteredSet(Set<E> set, Filter<E> setFilter) {
+		Set<E> filteredSet = new HashSet<E>();
+		for (E element : set) {
+			if (setFilter.filterObject(element)) {
+				filteredSet.add(element);
+			}
+		}
+		return filteredSet;
+	}
+
+	/**
+	 * Returns a map that contains only the elements from the given map that
+	 * match the given filter.
+	 *
+	 * @param <K>
+	 *            The type of the map keys
+	 * @param <V>
+	 *            The type of the map values
+	 * @param map
+	 *            The map to filter
+	 * @param mapFilter
+	 *            The map filter
+	 * @return The filtered map
+	 */
+	public static <K, V> Map<K, V> filteredMap(Map<K, V> map, Filter<Entry<K, V>> mapFilter) {
+		Map<K, V> filteredMap = new HashMap<K, V>();
+		for (Entry<K, V> element : map.entrySet()) {
+			if (mapFilter.filterObject(element)) {
+				filteredMap.put(element.getKey(), element.getValue());
+			}
+		}
+		return filteredMap;
+	}
+
+	/**
+	 * Returns a collection that contains only the elements from the given
+	 * collection that match the given filter.
+	 *
+	 * @param <K>
+	 *            The type of the collection values
+	 * @param collection
+	 *            The collection to filter
+	 * @param collectionFilter
+	 *            The collection filter
+	 * @return The filtered collection
+	 */
+	public static <K> Collection<K> filteredCollection(Collection<K> collection, Filter<K> collectionFilter) {
+		return filteredList(new ArrayList<K>(collection), collectionFilter);
+	}
+
+	/**
+	 * Returns an iterator that contains only the elements from the given
+	 * iterator that match the given filter.
+	 *
+	 * @param <E>
+	 *            The type of the iterator elements
+	 * @param iterator
+	 *            The iterator to filter
+	 * @param iteratorFilter
+	 *            The iterator filter
+	 * @return The filtered iterator
+	 */
+	public static <E> Iterator<E> filteredIterator(final Iterator<E> iterator, final Filter<E> iteratorFilter) {
+		return new Iterator<E>() {
+
+			private boolean gotNextElement = false;
+
+			private E nextElement;
+
+			private void getNextElement() {
+				if (gotNextElement) {
+					return;
+				}
+				while (iterator.hasNext()) {
+					nextElement = iterator.next();
+					if (iteratorFilter.filterObject(nextElement)) {
+						gotNextElement = true;
+						break;
+					}
+				}
+			}
+
+			/**
+			 * {@inheritDoc}
+			 *
+			 * @see java.util.Iterator#hasNext()
+			 */
+			public boolean hasNext() {
+				getNextElement();
+				return gotNextElement;
+			}
+
+			/**
+			 * {@inheritDoc}
+			 *
+			 * @see java.util.Iterator#next()
+			 */
+			public E next() {
+				getNextElement();
+				if (!gotNextElement) {
+					throw new NoSuchElementException("no more elements in iteration");
+				}
+				gotNextElement = false;
+				return nextElement;
+			}
+
+			/**
+			 * {@inheritDoc}
+			 *
+			 * @see java.util.Iterator#remove()
+			 */
+			public void remove() {
+				throw new UnsupportedOperationException("remove() not supported on this iteration");
+			}
+
+		};
+	}
+
+}
-- 
2.7.4