Why does my sorting loop seem to append an element where it shouldn t

Question

I am trying to sort an array of Strings using compareTo    This is my code   static String Array        Hello      This     is     Sorting     Example    String temp   public static void main String   args        for  int j 0  j lt Array length j                for  int i j 1   i lt Array length  i                        if  Array i  compareTo Array j   lt 0                              String temp   Array j                  Array j    Array i                  Array i    temp                               System out print Array j             Now the output is   Hello  This Example Sorting is   I am getting results  but not the results I want to get  which are   Hello This Example Is Sorting   How can I adjust my code to sort the string array properly

User · Answer

If you use   if  Array i  compareToIgnoreCase Array j    lt  0    you will get   Example  Hello  is  Sorting  This   which I think is the output you were looking for

User · Answer

Apart from the alternative solutions that were posted here  which are correct   no one has actually answered your question by addressing what was wrong with your code   It seems as though you were trying to implement a selection sort algorithm  I will not go into the details of how sorting works here  but I have included a few links for your reference      Your code was syntactically correct  but logically wrong  You were partially sorting your strings by only comparing each string with the strings that came after it  Here is a corrected version  I retained as much of your original code to illustrate what was  wrong  with it    static  String Array      Hello       This      is     Sorting     Example    String  temp     Keeps track of the smallest string s index int  shortestStringIndex    public static void main String   args                        I reduced the upper bound from Array length to  Array length - 1   for int j 0  j  lt  Array length - 1 j            shortestStringIndex   j        for  int i j 1   i lt Array length  i                      We keep track of the index to the smallest string          if Array i  trim   compareTo Array shortestStringIndex  trim    lt 0                          shortestStringIndex   i                             We only swap with the smallest string      if shortestStringIndex    j                  String temp   Array j            Array j    Array shortestStringIndex             Array shortestStringIndex    temp                Further Reading  The problem with this approach is that its asymptotic complexity is O n 2   In simplified words  it gets very slow as the size of the array grows  approaches infinity   You may want to read about better ways to sort data  such as quicksort

User · Answer

Your output is correct  Denote the white characters of    Hello  and   This  at the beginning   Another issue is with your methodology  Use the Arrays sort   method   String   strings       Hello      This     Is     Sorting     Example     Arrays sort strings     Output    Hello  This Example Is Sorting   Here the third element of the array  is  should be  Is   otherwise it will come in last after sorting  Because the sort method internally uses the ASCII value to sort elements

User · Answer

I know this is a late reply but maybe it can help someone   Removing whitespace can be done by using the trim   function  After that if you want to sort the array with case sensitive manner you can just use   Arrays sort yourArray     and for case insensitive manner   Arrays sort yourArray String CASE INSENSITIVE ORDER     Hope this helps

User · Answer

Instead of this line  if Array i  compareTo Array j   lt 0    use this line  if Array i  trim   compareTo Array j  trim    lt 0    and you are good to go   The reason your current code is not working is explained by other users already   This above replacement is one workaround amongst several that you could apply

User · Answer

Starting from Java 8  you can also use parallelSort which is useful if you have arrays containing a lot of elements   Example   public static void main String   args        String   strings      x    a    c    b    y         Arrays parallelSort strings       System out println Arrays toString strings          a  b  c  x  y      If you want to ignore the case  you can use   public static void main String   args        String   strings      x    a    c    B    y         Arrays parallelSort strings  new Comparator lt String gt               Override         public int compare String o1  String o2                              return o1 compareToIgnoreCase o2                         System out println Arrays toString strings          a  B  c  x  y      otherwise B will be before a   If you want to ignore the trailing spaces during the comparison  you can use trim     public static void main String   args        String   strings      x      a    c      b    y         Arrays parallelSort strings  new Comparator lt String gt               Override         public int compare String o1  String o2                              return o1 trim   compareTo o2 trim                           System out println Arrays toString strings          a   b  c   x  y      See    https   docs oracle com javase tutorial java nutsandbolts arrays html Difference between Arrays sort   and Arrays parallelSort   http   grepcode com file repository grepcode com java root jdk openjdk 8u40-b25 java util Arrays java av f

User · Answer

To begin with  your problem is that you use the method  compareTo   which is case sensitive  That means that the Capital letters are sorted apart from the lower case  The reason is that it translated in Unicode where the capital letters are presented with numbers which are less than the presented number of lower case  Thus you should use  compareToIgnoreCase    as many also mentioned in previous posts   This is my full example approach of how you can do it effecively  After you create an object  of the Comparator you can pass it in this version of  sort    which defined in java util Arrays   static lt T gt void sort T  array Comparator lt  super T gt comp    take a close look at super  This makes sure that the array which is passed into is combatible with the type of comparator   The magic part of this way is that you can easily sort the array of strings in Reverse order you can easily do by   return strB compareToIgnoreCase strA       import java util Comparator       public class IgnoreCaseComp implements Comparator lt String gt              Override         public int compare String strA  String strB                return strA compareToIgnoreCase strB                           import java util Arrays       public class IgnoreCaseSort            public static void main String   args                String strs        Hello      This     is     Sorting     Example                System out print  Initial order                   for  String s   strs                    System out print s                                    System out println   n                 IgnoreCaseComp icc   new IgnoreCaseComp                 Arrays sort strs  icc                System out print  Case-insesitive sorted order                   for  String s   strs                    System out print s                                    System out println   n                 Arrays sort strs                System out print  Default  case-sensitive sorted order                  for  String s   strs                    System out print s                                    System out println   n                          run      Initial order   Hello   This  is  Sorting  Example       Case-insesitive sorted order    Hello   This  Example is  Sorting        Default  case-sensitive sorted order   Hello   This  Example Sorting  is        BUILD SUCCESSFUL  total time  0 seconds    Alternative Choice  The method compareToIgnoreCase    although it works well with many occasions just like compare string in english  it will wont work well with all languages and locations  This automatically makes it an unfit choice for use  To make sure that it will be suppoorted everywhere you should use compare   from java text Collator   You can find a collator for your location by calling the method getInstance    After that you should set this Collator s strength property  This can be done with the setStrength   method together with Collator PRIMARY as parameter  With this alternative choise the IgnocaseComp can be written  just like below  This version of code will generate the same output independently of the location  import java text Collator  import java util Comparator     this comparator uses one Collator to determine    the right sort usage with no sensitive type    of the 2 given strings public class IgnoreCaseComp implements Comparator lt String gt         Collator col       IgnoreCaseComp               default locale         col   Collator getInstance               this will consider only PRIMARY difference   a  vs  b           col setStrength Collator PRIMARY               Override     public int compare String strA  String strB            return col compare strA  strB

User · Answer

Hello       This      is     Sorting     Example   First of all you provided spaces in   Hello   and   This    spaces have a lower value than alphabetic characters in Unicode  so it gets printed first   The rest of the characters were sorted alphabetically    Now upper case letters have a lower value than lower case letter in Unicode  so  Example  and  Sorting  gets printed  then at last  is   which has the highest value

[java] Why does my sorting loop seem to append an element where it shouldn't?

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