Check if collection has duplicates. - Java java.util

Java examples for java.util:Collection Contain

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Description

Check if collection has duplicates.

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(hasDuplicates(c));
    }//from w ww  .ja v a  2s.co m

    /**
     * Check if collection has duplicates. Two null values are also duplicates.
     * 
     * @param c
     *            to check for duplicates
     * @return true if collection has duplicates.
     */
    public static <E> boolean hasDuplicates(Collection<E> c) {
        Iterator<E> iterator = c.iterator();
        int idx = 0;
        while (iterator.hasNext()) {
            idx++;
            E e = iterator.next();
            // do not check last
            if (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 == s || (e != null && e.equals(s))) {
                        return true;
                    }
                }
            }
        }
        return false;
    }
}

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