Vowel-Substring(HackerRank-Problem Solving Assessment)

import java.io.*;
import java.math.*;
import java.security.*;
import java.text.*;
import java.util.*;
import java.util.concurrent.*;
import java.util.function.*;
import java.util.regex.*;
import java.util.stream.*;
import static java.util.stream.Collectors.joining;
import static java.util.stream.Collectors.toList;



class Result {

    /*
     * Complete the 'findSubstring' function below.
     *
     * The function is expected to return a STRING.
     * The function accepts following parameters:
     *  1. STRING s
     *  2. INTEGER k
     */

    public static String[] findSubstring(String s, int k) {
    // Write your code here

    char[] array = s.toCharArray();

    int a=0,b=k,previous_C=0;
    String previous_W="";
String[] array2 = new String[2];
int c=0;
for(int i=0;i<array.length;i++)
{
    
    if(array[i] == 'a' || array[i] == 'e' || array[i] == 'i' ||
        array[i] == 'o' || array[i] == 'u')
        {
            c++;
            break;

        }
        else
        {
            if(c!=0)
            array2[0] = "Not found!";
        }

}

if(c!=0){
    while(a!=(array.length-k+1)){
    
    int count=0;
String word = "";

    for(int i=a;i<b;i++)
    {
        if(array[i] == 'a' || array[i] == 'e' || array[i] == 'i' ||
        array[i] == 'o' || array[i] == 'u')
        {
            count++;
        }

        while(i==0){
            previous_C = count;
            break;
        }
        word += ""+array[i];
    }
        while(a==0){
        previous_W = word.toString();
        break;
        }
        a++;
        b++;
        
        if(count>previous_C && previous_C !=0)
        {
            previous_C = count;
            previous_W = word.toString();
        }
     //***   
    }
}
if(c!=0)
{
array2[0]=previous_W;
}



array2[1]=(String.valueOf(previous_C));
        return array2;
    }

}

public class Solution {
    public static void main(String[] args) throws IOException {
        System.gc();
        Scanner sc = new Scanner(System.in);

        String s =sc.nextLine();

        int k = sc.nextInt();

        String[] result = Result.findSubstring(s, k);
        if(result[0] == null)
        {
        System.out.println("Not found!");    
        }else{
        System.out.println(result[0]);
        }// System.out.println(result[1]);
        System.gc();
    }
}