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Making libGDX's data structures implement JDK interfaces.
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/*
 * Copyright (c) 2013-2025 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.github.tommyettinger.ds.support.util;

import com.github.tommyettinger.function.DoubleConsumer;

import java.util.Iterator;
import java.util.NoSuchElementException;

/**
 * An Iterator specialized for {@code double} values.
 * This iterates over primitive doubles using {@link #nextDouble()}.
 * 

 * This is roughly equivalent to {@code DoubleIterator} in Java 8, and is present here so environments
 * don't fully support Java 8 APIs (such as RoboVM) can use it.
 * 

 * This interface is closely based on {@code DoubleIterator} in OpenJDK 8.
 * This iterator interface is extremely simple and there's no way to implement it in a way
 * that respects compatibility other than the way OpenJDK 8 does.
 * OpenJDK's
 * license is available here,
 * if it applies at all.
 */
public interface DoubleIterator extends Iterator {
	/**
	 * Returns the next {@code double} element in the iteration.
	 *
	 * @return the next {@code double} element in the iteration
	 * @throws NoSuchElementException if the iteration has no more elements
	 */
	double nextDouble ();

	/**
	 * Performs the given action for each remaining element until all elements
	 * have been processed or the action throws an exception.  Actions are
	 * performed in the order of iteration, if that order is specified.
	 * Exceptions thrown by the action are relayed to the caller.
	 *
	 * @param action The action to be performed for each element
	 * @throws NullPointerException if the specified action is null
	 * @implSpec The default implementation behaves as if:
	 * 
{@code
	 *     while (hasNext())
	 *         action.accept(nextDouble());
	 * }
	 */
	default void forEachRemaining (DoubleConsumer action) {
		while (hasNext()) {action.accept(nextDouble());}
	}

	/**
	 * {@inheritDoc}
	 *
	 * @implSpec The default implementation boxes the result of calling
	 * {@link #nextDouble()}, and returns that boxed result.
	 */
	@Override
	default Double next () {
		return nextDouble();
	}
}