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package net.sf.saxon.tree.iter;

import java.util.Iterator;

/**
 * A Java Iterator which applies a mapping function to each item in an input sequence
 * @param  the type of the input items
 * @param  the type of the delivered item
 */


public class MappingJavaIterator implements Iterator {

    private Iterator input;
    private Mapper mapper;

    /**
     * Create a mapping iterator
     * @param in the input sequence
     * @param mapper the mapping function to be applied to each item in the ipnut sequence to
     *               generate the corresponding item in the result sequence
     */

    public MappingJavaIterator(Iterator in, Mapper mapper) {
        this.input = in;
        this.mapper = mapper;
    }

    public boolean hasNext() {
        return input.hasNext();
    }

    public T next() {
        while (true) {
            T next = mapper.map(input.next());
            if (next != null) {
                return next;
            }
        }
    }

    public void remove() {
        input.remove();
    }

    /**
     * Interface defining the mapping function
     * @param  the type of the input items
     * @param  the type of the output items
     */

    public interface Mapper {
        /**
         * Map one input item to one output item
         * @param in the input item
         * @return an output item, or null. Any nulls are omitted from the result sequence delivered by the mapping
         * iterator.
         */
        T map(S in);
    }
}