Return first duplicate value that is not null, or null if there is no such value. - Java java.util

Java examples for java.util:Collection Null Element

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Description

Return first duplicate value that is not null, or null if there is no such value.

Demo Code


//package com.book2s;

import java.util.Collection;
import java.util.Iterator;

public class Main {
    public static void main(String[] argv) {
        Collection c = java.util.Arrays.asList("asdf", "book2s.com");
        System.out.println(firstDuplicateValue(c));
    }//from   w  w w.  j a v  a 2 s .  c om

    /**
     * Return first duplicate value that is not null, or null if there is no
     * such value. Even logic is similar to hasDuplicateValues, code had to be
     * duplicated because of different handling of null.
     * 
     * @param c
     *            to search for duplicate value
     * @return first duplicate value
     */
    public static <E> E firstDuplicateValue(Collection<E> c) {
        Iterator<E> iterator = c.iterator();
        int idx = 0;
        while (iterator.hasNext()) {
            idx++;
            E e = iterator.next();
            if (e != null && iterator.hasNext()) {
                Iterator<E> subiterator = c.iterator();
                // move subiterator to index
                int sub = 0;
                while (subiterator.hasNext() && sub < idx) {
                    sub++;
                    subiterator.next();
                }
                // check if others are duplicates
                while (subiterator.hasNext()) {
                    E s = subiterator.next();
                    if (e.equals(s)) {
                        return e;
                    }
                }
            }
        }
        return null;
    }
}

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