Finding duplicate values in array. java

Question

Possible Duplicate:
How to find a duplicate of length 5 in a single array. Java

I am trying to see if there are any duplicates in the array.

import java.util.Hashtable;

public class test {
    static final int COUNT = 10;

    static Hashtable<String, Integer> compareSet = new Hashtable<String, Integer>();
    static String groupInteger = "";
    static long arr[] = new long[5];
    static int st = 1;
    static int end = 56;
    static double t1;
    static double t2;

    static int ctr = 0;

    public static void main(String[] args) {
        t1 = System.currentTimeMillis();
        for (int n = 0; n < COUNT; n++) {
            for (int i = 0; i < arr.length; i++) {
                arr[i] = (long) ((Math.random() * (end - st + 1)) + st);

            }
            for (int i = 0; i < 5; i++) {
                groupInteger += arr[i];
                if (i % 5 == 0) {
                    System.out.println();
                    if (compareSet.containsKey(groupInteger)) {
                        ctr++;
                        System.out.println("duplicate found ");
                        int currentCount = compareSet.get(groupInteger);
                        compareSet.put(groupInteger, currentCount + 1);

                    } else {
                        compareSet.put(groupInteger, 1);
                    }
                    groupInteger = "";
                }
                System.out.print(arr[i]);
            }
        }
        t2 = System.currentTimeMillis();
        System.out.println();
        System.out.println();
        System.out.println("\t" + "Total run time is " + ((t2 - t1)) + "ms");
        System.out.println(compareSet);
    }
}

the console:

12  23  8   44  23
28  13  39  49  53
37  40  16  53  48
6   45  14  52  20
32  4   41  10  38
38  29  25  21  13
16  34  45  26  11
22  33  54  21  10
40  34  53  37  50
20  26  48  32  51

I want to be able to check if there are duplicate rows. I cant seem to finagle this code around to work properly. Please let me know if you see something! Thank you

do you at least understand the code he gave you? http://stackoverflow.com/questions/9893580/how-to-find-a-duplicate-of-length-5-in-a-single-array-java — talnicolas, Mar 27 '12 at 18:53
i understand, the array is generated randomly with numbers between 1-56 every time i run the program i get different values. and i'm printing close to 100,000 thousand rows. I want to be able to tell how many times there is a duplicate. — Eric Goncalves, Mar 27 '12 at 18:54
but have you tested with a simple test that if there are two duplicate rows they are found or not? — talnicolas, Mar 27 '12 at 18:55
it finds duplicates, but when i print compareSet, the arrays are off; for example, {1917454822=1, 48326949=1, 502272218=1, 61612212=1, 72812428=1, 5244323532=1, 2=1, 5521371113=1, 567311247=1, 41436725=1} — Eric Goncalves, Mar 27 '12 at 18:56
let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/9377/discussion-between-eric-and-talnicolas) — Eric Goncalves, Mar 27 '12 at 19:01
Easiest way is once you populate the elements write it out to a string or an array and parse element by element by adding it to hashmap/hashset. makes sense? — Venki, Mar 27 '12 at 19:05
no, it doesnt haha. Ive never used or heard of hashmap or hashset. the hash part of the code was recommended by someone else on stackoverflow. — Eric Goncalves, Mar 27 '12 at 19:08
Please refrain from reposting your questions. If you have details to add, edit the original question instead. — NullUserException, Mar 30 '12 at 01:11

stefan bachert · Accepted Answer · 2012-03-27T19:19:07.093

You are using inappropriate classes for that, if you want to find "any" duplicates Use HashSet<String>

And your code is totally buggy. The if-then part must be after the for, without if.

HashSet<String> compareSet = new HashSet<String> ();
...
groupInteger.empty ();
for (int i = 0; i < 5; i++) {
  groupInteger += arr[i] + " ";
}
System.out.println(groupInteger);
if (compareSet.contains(groupInteger)) {
    System.out.println("duplicate found ");
} else {
    compareSet.add(groupInteger);
}

And if you want to "count" duplicates, I would use HashMap

HashMap<String, Integer> compareSet = new HashMapt<String, Integer> ();
...
Integer act = compareSet.get(groupInteger);
if (act != null) {
    System.out.println("duplicate found ");
    compareSet.put(groupInteger, act + 1);
} else {
    compareSet.put(groupInteger, 1);
}

that fixed it, however, it doesn't show how many times it appears. — Eric Goncalves, Mar 27 '12 at 19:13

Finding duplicate values in array. java

1 Answers1