How to find duplicate char value from a String in a String array

Question

I am trying to display duplicate string from an array but the code is not working.For example:In the word "arrow" r is coming two times shoq the code should display the output 'r'.But it is not displaying anything

public class duplicatearray {
        public static void main(String[] args)
        {
            String[] s={"arrow"};
            for(int i=0;i<s.length;i++)
            {
                for(int j=i+1;j<s.length;j++)
                {
                    if(s[i].equals(s[j]))
                    {
                        System.out.println("Duplicate value"+s[i]);
                    }
                }
            }

        }
    }

You are checking against String Array. Do you need this array? or you need only one string. — Prathibha Chiranthana
– Prathibha Chiranthana, Commented Feb 8, 2018 at 6:22
Your question title and description have no match. And I edited your title after reading the description. Feel free to revert it back if that makes no sense. — Suresh Atta
– Suresh Atta, Commented Feb 8, 2018 at 6:28
@PrathibhaChiranthana From the example, I guess in a String, duplicate char's — Suresh Atta
– Suresh Atta, Commented Feb 8, 2018 at 6:32
@ꜱᴜʀᴇꜱʜᴀᴛᴛᴀ String[] s={"arrow"}; was confused. — Prathibha Chiranthana
– Prathibha Chiranthana, Commented Feb 8, 2018 at 6:35
@PrathibhaChiranthana What so tricky in it ? It is just a String array with only one element — Suresh Atta
– Suresh Atta, Commented Feb 8, 2018 at 6:38

Suresh Atta · Accepted Answer · 2018-02-08 06:22:26Z

1

For example:In the word "arrow" r is coming two times shoq the code should display the output 'r'.

You are checking your checking two Strings. Where as you want to check for duplicate characters

if(s[i].equals(s[j]))

It should be

if(s[i].charAt(j) == s[i].charAt(j+1))

Then it check against characters in the same Strings. And also in the print statement

System.out.println("Duplicate value"+s[i].charAt(j));

And you loop also wrong, you should start at 0'th character

for(int j= 0 ;j<s[i].length() -1 ;j++)

So overall it should be

String[] s = { "arrow" };
for (int i = 0; i < s.length; i++) {
    for (int j = 0; j < s[i].length() - 1; j++) {
        if (s[i].charAt(j) == s[i].charAt(j + 1)) {
            System.out.println("Duplicate value : " + s[i].charAt(j));
        }
    }
}

edited Feb 8, 2018 at 6:22

answered Feb 8, 2018 at 6:21

Suresh Atta

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4 Comments

absin Over a year ago

I am trying to display duplicate string from an array, I think the question clearly states otherwise

Suresh Atta Over a year ago

@AbSin Right. The Question and the description have mismatched.

absin Over a year ago

Yeah I notice too, shouldn't have doubted you.

Suresh Atta Over a year ago

@AbSin No problem. The title and description are messy anyway :D

Prathibha Chiranthana · Accepted Answer · 2018-02-08 06:34:41Z

Try with below code snippet It will give you what is expected.

    public static void main(String[] args) {

            String[] s = {"arrow"};
            for (int k =0; k < s.length; k++) {

            char[] arr = s[k].toCharArray();//get char array

            for (int i = 0; i < arr.length; i++) // 1
            {
                int duplicateCount = 0;
                for (int j = 1; j < arr.length; j++) {
                    if (arr[i] == (arr[j])) {
                        duplicateCount++;//duplicate variable
                        if (duplicateCount >= 2)
                            System.out.println("Duplicate value " + arr[i]);
                    }
                }
            }
        }
    }

Jayanth · Accepted Answer · 2018-02-08 06:41:02Z

I see a flaw in your code.

String[] s={"arrow"};

you need not declare this as an array. Just a string is suffice.If you call s[i] on this, it will always return "arrow" not 'a' or 'r' as you are expecting. You had to have a char[] for it.

Anyhow, i used your input in my code and printed out the necessary statements. Go through it. Hope it helps.

Try with HashSet. It gives better performance.

import java.util.Collection;
import java.util.HashSet;


public class duplicate {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        String[] s={"arrow"};
        System.out.println(s[0]);
        HashSet<Character> hash = new HashSet<Character>();
        char[] s1 = s[0].toCharArray();
        for(char c : s1){
            if(!(hash.add(c)))
                System.out.println(c);
        }

    }

}

Praveen Kumar · Accepted Answer · 2018-02-08 09:50:16Z

0

your code is using two for loops which can take more time as string size increases. try with below code snippet

public class DuplicateArray {
    public static void main (String...args) {
        String str = new String("arrow");
        int[] dupArray = new int[256];
        for (int i=0;i<str.length();i++) {
            char ch = str.charAt(i);
            if (dupArray[ch] == 0) {
                dupArray[ch]++;
            } else {
                System.out.println("Duplicate value : "+ch+" ");
            }
        }
    }
}

answered Feb 8, 2018 at 9:50

Praveen Kumar

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