You are given an array strarr of strings and an integer k. Your task is to return the first longest string consisting of k consecutive strings taken in the array.

Example: longest_consec(["zone", "abigail", "theta", "form", "libe", "zas", "theta", "abigail"], 2) --> "abigailtheta"

n being the length of the string array, if n = 0 or k > n or k <= 0 return "".

Good Solution1:

class LongestConsec {
    public static String longestConsec(String[] strarr, int k) {
        if (strarr.length == 0 || k > strarr.length || k <= 0)
            return "";

        String longestStr = "";
        for (int index = 0; index < strarr.length - k + 1; index++) {
            StringBuilder sb = new StringBuilder();
            for (int i = index; i < index + k; i++) {
                sb.append(strarr[i]);
            }
            if (sb.toString().length() > longestStr.length()) {
                longestStr = sb.toString();
            }
        }
        return longestStr;
    }
}

Good Solution2:

import java.util.stream.*;
class LongestConsec {
  public static String longestConsec(String[] strarr, int k) {
    String maxStr = "";
    for (int i=0; i<=strarr.length-k; i++) {
      String current = IntStream.range(i, i+k).mapToObj(j -> strarr[j]).collect(Collectors.joining());
      if (current.length() > maxStr.length()) maxStr = current;
    }
    return maxStr;
  }
}