com.badlogic.gdx.utils.Predicate Maven / Gradle / Ivy
/*******************************************************************************
* Copyright 2011 See AUTHORS file.
*
* 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 com.badlogic.gdx.utils;
import java.util.Iterator;
/** Interface used to select items within an iterator against a predicate.
* @author Xoppa */
public interface Predicate {
/** @return true if the item matches the criteria and should be included in the iterator's items */
boolean evaluate (T arg0);
public class PredicateIterator implements Iterator {
public Iterator iterator;
public Predicate predicate;
public boolean end = false;
public boolean peeked = false;
public T next = null;
public PredicateIterator (final Iterable iterable, final Predicate predicate) {
this(iterable.iterator(), predicate);
}
public PredicateIterator (final Iterator iterator, final Predicate predicate) {
set(iterator, predicate);
}
public void set (final Iterable iterable, final Predicate predicate) {
set(iterable.iterator(), predicate);
}
public void set (final Iterator iterator, final Predicate predicate) {
this.iterator = iterator;
this.predicate = predicate;
end = peeked = false;
next = null;
}
@Override
public boolean hasNext () {
if (end) return false;
if (next != null) return true;
peeked = true;
while (iterator.hasNext()) {
final T n = iterator.next();
if (predicate.evaluate(n)) {
next = n;
return true;
}
}
end = true;
return false;
}
@Override
public T next () {
if (next == null && !hasNext()) return null;
final T result = next;
next = null;
peeked = false;
return result;
}
@Override
public void remove () {
if (peeked) throw new GdxRuntimeException("Cannot remove between a call to hasNext() and next().");
iterator.remove();
}
}
public static class PredicateIterable implements Iterable {
public Iterable iterable;
public Predicate predicate;
public PredicateIterator iterator = null;
public PredicateIterable (Iterable iterable, Predicate predicate) {
set(iterable, predicate);
}
public void set (Iterable iterable, Predicate predicate) {
this.iterable = iterable;
this.predicate = predicate;
}
/** Returns an iterator. Remove is supported.
*
* If {@link Collections#allocateIterators} is false, the same iterator instance is returned each time this method is called. Use
* the {@link Predicate.PredicateIterator} constructor for nested or multithreaded iteration. */
@Override
public Iterator iterator () {
if (Collections.allocateIterators) return new PredicateIterator(iterable.iterator(), predicate);
if (iterator == null)
iterator = new PredicateIterator(iterable.iterator(), predicate);
else
iterator.set(iterable.iterator(), predicate);
return iterator;
}
}
}