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JHotDraw8 Utility classes for Collections

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/*
 * @(#)MappedSpliterator.java
 * Copyright © 2023 The authors and contributors of JHotDraw. MIT License.
 */

package org.jhotdraw8.collection.mapped;

import org.jspecify.annotations.Nullable;

import java.util.Spliterator;
import java.util.function.Consumer;
import java.util.function.Function;

/**
 * Maps a {@link Spliterator} to a different element type.
 * 
 * The underlying iterator is referenced - not copied.
 *
 * @param  the mapped element type
 * @param  the original element type
 * @author Werner Randelshofer
 */
public class MappedSpliterator implements Spliterator {
    private final Spliterator s;
    private final Function mappingFunction;
    private final int characteristics;

    public MappedSpliterator(Spliterator s, Function mappingFunction, int characteristics) {
        this.s = s;
        this.mappingFunction = mappingFunction;
        this.characteristics = characteristics;
    }

    public MappedSpliterator(Spliterator s, Function mappingFunction) {
        this(s, mappingFunction, s.characteristics());
    }

    @Override
    public boolean tryAdvance(Consumer action) {
        return s.tryAdvance(k -> action.accept(mappingFunction.apply(k)));
    }

    @Override
    public @Nullable Spliterator trySplit() {
        Spliterator split = s.trySplit();
        return split == null ? null : new MappedSpliterator<>(split, mappingFunction, characteristics);
    }

    @Override
    public long estimateSize() {
        return s.estimateSize();
    }

    @Override
    public int characteristics() {
        return characteristics;
    }
}