Ne ponial ya zadanie ili...?
package com.javarush.task.task39.task3901;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.HashSet;
import java.util.Set;
import java.util.TreeSet;
/*
Уникальные подстроки
*/
public class Solution {
public static void main(String[] args) throws IOException {
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
System.out.println("Please enter your string: ");
String s = bufferedReader.readLine();
System.out.println("The longest unique substring length is: \n" + lengthOfLongestUniqueSubstring(s));
}
public static Integer lengthOfLongestUniqueSubstring(String s) {
if (s.length()==0) return 0;
if (s==null) return null;
TreeSet<Character> set = new TreeSet<>();
for (int i = 0; i < s.length() ; i++) {
Character c = s.charAt(i);
set.add(c);
}
return set.size();
}
}