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

Answer 1

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);
}