Java Stream Operation zipWithIndex(Stream stream, int startIndex)

Description

Zips the specified stream with its indices.

License

Open Source License

Declaration

public static <T> Stream<Map.Entry<Integer, T>> zipWithIndex(Stream<? extends T> stream, int startIndex) 

Method Source Code

//package com.java2s;
/*//w w  w. ja v  a  2s. co m
 * Copyright 2015 Alfresco Software, Ltd.  All rights reserved.
 *
 * License rights for this program may be obtained from Alfresco Software, Ltd. 
 * pursuant to a written agreement and any use of this program without such an 
 * agreement is prohibited. 
 */

import java.util.AbstractMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Spliterator;
import java.util.Spliterators;

import java.util.stream.Stream;
import java.util.stream.StreamSupport;

public class Main {
    /**
     * Zips the specified stream with its indices.
     */
    public static <T> Stream<Map.Entry<Integer, T>> zipWithIndex(Stream<? extends T> stream, int startIndex) {
        return iterate(new Iterator<Map.Entry<Integer, T>>() {
            private final Iterator<? extends T> streamIterator = stream.iterator();
            private int index = startIndex;

            @Override
            public boolean hasNext() {
                return streamIterator.hasNext();
            }

            @Override
            public Map.Entry<Integer, T> next() {
                return new AbstractMap.SimpleImmutableEntry<>(index++, streamIterator.next());
            }
        });
    }

    /**
     * Converts an {@link java.util.Iterator} to {@link java.util.stream.Stream}.
     */
    public static <T> Stream<T> iterate(Iterator<? extends T> iterator) {
        int characteristics = Spliterator.ORDERED | Spliterator.IMMUTABLE;
        return StreamSupport.stream(Spliterators.spliteratorUnknownSize(iterator, characteristics), false);
    }
}

Related

1. toParameter(Stream input, Class exp)
2. toString(IntStream s)
3. toString(LongStream ls)
4. upcastStream(Stream stream)
5. zip(List> streams)