Java Substring Comparisons

We define the following terms:

• Lexicographical Order, also known as alphabetic or dictionary order, orders characters as follows: 
  For example, ball < cat, dog < dorm, Happy < happy, Zoo < ball.
• A substring of a string is a contiguous block of characters in the string. For example, the substrings of abc are a, b, c, ab, bc, and abc.

Given a string, , and an integer, , complete the function so that it finds the lexicographically smallest and largestsubstrings of length .

Input Format

The first line contains a string denoting .
The second line contains an integer denoting .

Constraints

•  consists of English alphabetic letters only (i.e., [a-zA-Z]).

Output Format

Return the respective lexicographically smallest and largest substrings as a single newline-separated string.

Sample Input 0

welcometojava
3

Sample Output 0

ava
wel

Explanation 0

String  has the following lexicographically-ordered substrings of length :

We then return the first (lexicographically smallest) substring and the last (lexicographically largest) substring as two newline-separated values (i.e., ava\nwel).

The stub code in the editor then prints ava as our first line of output and wel as our second line of output.

import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {
  
    public static String getSmallestAndLargest(String s, int k) {
        String smallest = "";
        String largest = "";
        
        // Complete the function
        // 'smallest' must be the lexicographically smallest substring of length 'k'
        // 'largest' must be the lexicographically largest substring of length 'k'
        for(int i = 0;i<=s.length()-k;i++){
             String subString = s.substring(i,i+k);
             if(i == 0){
                 smallest = subString;
             }
             if(subString.compareTo(largest)>0){
                 largest = subString;
             }else if(subString.compareTo(smallest)<0)
                 smallest = subString;
      }
        
        return smallest + "\n" + largest;
    }

    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        String s = scan.next();
        int k = scan.nextInt();
        scan.close();
      
        System.out.println(getSmallestAndLargest(s, k));
    }
}