• Source 
    1. import java.util.*;
    2.  
    3. class Main
    4. {
    5.     public static boolean hasUniqueChars(String toTest)
    6.     {
    7.         char charArray[] = toTest.toCharArray();
    8.         Arrays.sort(charArray);
    9.  
    10.         for (int x = 1; x < charArray.length; x++)
    11.         {
    12.             if ( charArray[x] == charArray[x-1] )
    13.                 return false;
    14.         }
    15.  
    16.         return true;
    17.     }
    18.  
    19.  
    20.     public static void main(String args[])
    21.     {
    22.         String testData[] = {
    23.             "abc",
    24.             "abcc",
    25.             "abcdefhi",
    26.             "abcdefhiabcdefhi",
    27.             "ccc",
    28.             "xxxkjsdfkjqqqdkjfd",
    29.             "abcdefghijklmnopqrstuvwxyz",
    30.         };
    31.  
    32.         for (String test : testData)
    33.         {
    34.             if ( hasUniqueChars(test) )
    35.             {
    36.                 System.out.println("  hasUniqueChars(\"" + test + "\")");
    37.             }
    38.             else
    39.             {
    40.                 System.out.println("! hasUniqueChars(\"" + test + "\")");
    41.             }
    42.         }
    43.     }
    44. }
    45.  
    46. // vim: sw=4:ts=4:sts=4:et:ai: