Find all repeated values

Question

I am writing a code to find duplicate values which have been entered in an array. But i am not able to get code right. Can anyone suggest me with an improvised code then this (using Arraylist)?

package com.Test1.java; 

import java.util.Arrays;
import java.util.Scanner;

public class Test1 {
    private static Scanner s;
    public static void main(String[] args) {
    int n;
    s = new Scanner(System.in);
    System.out.println("Enter the number of values you want to enter:");
    n=s.nextInt();
    int number[]=new int[n];
    System.out.println("Enter the values:");
        for(int i=1;i<=number.length;i++)
        {
            number[i]=s.nextInt();
            }
    System.out.println(“The Values Entered Are:”);
    Arrays.sort(number);
    for(int j=1;j<=number.length;j++)
    {
    if(number[j]==number[j-1])
    {
        System.out.println("The dupliclate number is"+number[j]);
    }

        }
    }
    }

I am getting this error output:

How many values you want to Enter: 
5
Enter the values:
1
2
2
3
4
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 5
    at com.Test1.java.Test1.main(Test1.java:17)**

Array are 0 indexed in Java. So instead of iterating from 1 to array.lenth, you must iterate from 0 to array.length-1 — Julien, Oct 27 '14 at 15:01
Possible duplicate of http://stackoverflow.com/questions/17967114/how-to-remove-duplicates-from-an-array-in-java — Chiseled, Oct 27 '14 at 15:06

score 3 · Accepted Answer · answered Oct 27 '14 at 15:06

Try this approach:

Turn the array into a List.
Turn the List into a Set to get each member once.
Check if each member of the Set is in the List more than once.

Java code:

import java.util.Arrays;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

public class SOPlayground {

    public static void main(String[] args) throws Exception {
        Integer numbers[] = new Integer[]{1, 3, 4, 6, 7, 9, 0, 9, 8, 6, 5, 4, 3, 2, 1};

        List<Integer> a = Arrays.asList(numbers);
        Set<Integer> s = new HashSet(a);
        for (Integer i : s) {
            if (Collections.frequency(a, i) > 1) {
                System.out.println(i + " is a duplicate");
            }
        }
    }
}

Output:

1 is a duplicate
3 is a duplicate
4 is a duplicate
6 is a duplicate
9 is a duplicate

Yes, that is possible. Did you try to buil an `Integer[]` using a `Scanner`? — , Oct 28 '14 at 07:41

tobias_k · Answer 2 · 2014-10-27T15:08:31.360

0

This answer (intentionally) does not provide a full alternative solution using ArrayLists, but instead tries to explain what's wrong with your array-based code, so you can fix it yourself. The problem is here:

for(int i=1;i<=number.length;i++)
{
    number[i]=s.nextInt();
}

In Java (and most other languages) the first index of an array of length n is 0, and the last index is n-1, not 1 and n. Thus, your loop should be

for (int i=0; i < number.length; i++)

And similar for your second for loop.

edited Oct 27 '14 at 15:08

answered Oct 27 '14 at 15:03

tobias_k

81,265
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1

Its not my downvote, but if he change the forloop like this, he will get the same error in this line: `number[j-1]` – kai Oct 27 '14 at 15:06
I think its clear for him that this only works if duplicate numbers are right next to each other, thats the reason why he is using `Arrays.sort(number);` – kai Oct 27 '14 at 15:10
Can anyone suggest me with an improvised code, i want to use a array list to get input. – Ganesh Karuppaiha Oct 27 '14 at 15:10
@kai You are right, did not see that line. Removed that remark. – tobias_k Oct 27 '14 at 15:11
I did the same for both the loops but still I get an error – Ganesh Karuppaiha Oct 27 '14 at 17:15
@GaneshKaruppaiha I just tried it, changed the first loop to `i=0;i – tobias_k Oct 27 '14 at 19:59

score -1 · Answer 3 · answered Oct 27 '14 at 15:03

-1

Array indexes in JAVA start from 0. Your for loop starts from 1 and goes up to 5 and is incorrect. Hence you're getting ArrayIndexOutOfBounds exception when you try to access number[5]

for(int i=1;i<=number.length;i++)

It should start from 0.

for(int i = 0; i < number.length; i++)

answered Oct 27 '14 at 15:03

harun

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This is a reasonable answer to explain why the OP is getting ArrayIndexOutOfBounds. why is the downvote? – harun Oct 27 '14 at 15:06

Find all repeated values

3 Answers3