Java Challenge - Unique Characters in a String

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import java.util.*;

public class UniqueCharacters {
  public static void main(String[] args) {
    System.out.println(uniqueCharacters(""));
  }

  public static boolean uniqueCharacters(String strIn) {
    if (strIn.length() == 0) {
      System.out.println("Error");
      return true;
    }
    ArrayList<String> list = new ArrayList<String>();
    for (int i = 0; i < strIn.length(); i++) {
      if (list.contains("" + strIn.charAt(i))) {
        return false;
      }
      list.add("" + strIn.charAt(i));
    }
    return true;
  }
}

This is what I keep trying as my solution, but it doesn’t work for some reason. I keep getting 4/5 tests correct. I suspect it has something to do with this part of the questions: “Note that if the function is called with an empty string (”“), the program should return an error message.” I’m not really sure how to deal with this as you can’t throw an exception of the tester will break, printing a string isn’t enough, and you can’t change the return type from boolean without the tester breaking. Anyone have an answer?

I pass same 4/5. Not sure where the problem is.

import java.util.*;

public class UniqueCharacters {
  public static void main(String[] args) {
    System.out.println(uniqueCharacters("apple"));
  }

  public static boolean uniqueCharacters(String strIn) {
        if(strIn == null || strIn.isEmpty()){
            System.out.println("Bad string");
            return false;
        }
        for (int i = 0; i < strIn.length() - 1; i++) {
            for (int j = i + 1; j < strIn.length(); j++) {
                if (strIn.charAt(i) == strIn.charAt(j)) {
                    return false;
                }
            }
        }
        return true;
    }

}

To pass all tests program should not return a boolean along with the error message if the inputted string is blank.


import java.util.*;
public class UniqueCharacters {
  public static void main(String[] args) {
    System.out.println(uniqueCharacters(""));
  }
  public static boolean uniqueCharacters(String strIn) {
  if (strIn == "")
  {
    System.out.println("Error"); 
    System.exit(0); // if string is blank, return error and end program
  }
    char[] strToArray = strIn.toCharArray(); // convert string to char array
    Arrays.sort(strToArray); // sort array alphabetically
    boolean result = true; // declare boolean result variable and set to true.
    // loop through array - compare index i with index i + 1 - bool set to false if they match
    for(int i = 0; i < strToArray.length - 1; i++)
    {
      if (strToArray[i] == strToArray[i+1])
      {
        result = false; 
      }        
    }
    return result;
  }
}
3 Likes

Thank you so much, this works

2 Likes