114 lines
3.3 KiB
Java
114 lines
3.3 KiB
Java
/*******************************************************************************
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* Copyright 2011 LibGDX.
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* Mario Zechner <badlogicgames@gmail.com>
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* Nathan Sweet <nathan.sweet@gmail.com>
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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******************************************************************************/
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package dorkbox.collections;
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import java.util.Iterator;
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/** Interface used to select items within an iterator against a predicate.
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* @author Xoppa */
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public interface Predicate<T> {
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/** @return true if the item matches the criteria and should be included in the iterator's items */
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boolean evaluate (T arg0);
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public class PredicateIterator<T> implements Iterator<T> {
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public Iterator<T> iterator;
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public Predicate<T> predicate;
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public boolean end = false;
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public boolean peeked = false;
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public T next = null;
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public PredicateIterator (final Iterable<T> iterable, final Predicate<T> predicate) {
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this(iterable.iterator(), predicate);
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}
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public PredicateIterator (final Iterator<T> iterator, final Predicate<T> predicate) {
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set(iterator, predicate);
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}
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public void set (final Iterable<T> iterable, final Predicate<T> predicate) {
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set(iterable.iterator(), predicate);
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}
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public void set (final Iterator<T> iterator, final Predicate<T> predicate) {
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this.iterator = iterator;
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this.predicate = predicate;
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end = peeked = false;
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next = null;
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}
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@Override
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public boolean hasNext () {
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if (end) return false;
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if (next != null) return true;
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peeked = true;
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while (iterator.hasNext()) {
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final T n = iterator.next();
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if (predicate.evaluate(n)) {
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next = n;
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return true;
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}
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}
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end = true;
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return false;
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}
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@Override
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public T next () {
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if (next == null && !hasNext()) return null;
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final T result = next;
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next = null;
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peeked = false;
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return result;
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}
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@Override
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public void remove () {
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if (peeked) throw new RuntimeException("Cannot remove between a call to hasNext() and next().");
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iterator.remove();
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}
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}
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public static class PredicateIterable<T> implements Iterable<T> {
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public Iterable<T> iterable;
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public Predicate<T> predicate;
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public PredicateIterator<T> iterator = null;
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public PredicateIterable (Iterable<T> iterable, Predicate<T> predicate) {
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set(iterable, predicate);
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}
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public void set (Iterable<T> iterable, Predicate<T> predicate) {
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this.iterable = iterable;
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this.predicate = predicate;
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}
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/** Returns an iterator. Note that the same iterator instance is returned each time this method is called. Use the
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* {@link Predicate.PredicateIterator} constructor for nested or multithreaded iteration. */
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@Override
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public Iterator<T> iterator () {
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if (iterator == null)
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iterator = new PredicateIterator<T>(iterable.iterator(), predicate);
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else
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iterator.set(iterable.iterator(), predicate);
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return iterator;
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}
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}
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}
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