Sort a two dimensional array based on one column

Question

In Java  I have a data in my array like the following  2009 07 25 20 24 Message A 2009 07 25 20 17 Message G 2009 07 25 20 25 Message B 2009 07 25 20 30 Message D 2009 07 25 20 01 Message F 2009 07 25 21 08 Message E 2009 07 25 19 54 Message R   I would like to sort it based on the first column  so my final data can look like this  2009 07 25 19 54 Message R 2009 07 25 20 01 Message F 2009 07 25 20 17 Message G 2009 07 25 20 24 Message A 2009 07 25 20 25 Message B 2009 07 25 20 30 Message D 2009 07 25 21 08 Message E   The first column is a date of format  yyyy MM dd HH mm  and the second column is a String

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Using Lambdas since java 8  final String     data   new String       new String      quot 2009 07 25 20 24 quot    quot Message A quot             new String      quot 2009 07 25 20 17 quot    quot Message G quot     new String      quot 2009 07 25 20 25 quot    quot Message B quot             new String      quot 2009 07 25 20 30 quot    quot Message D quot     new String      quot 2009 07 25 20 01 quot    quot Message F quot             new String      quot 2009 07 25 21 08 quot    quot Message E quot     new String      quot 2009 07 25 19 54 quot    quot Message R quot       String     out   Arrays stream data  sorted Comparator comparing x - gt  x 1    toArray String      new    System out println Arrays deepToString out          Output     2009 07 25 20 24  Message A     2009 07 25 20 25  Message B    2009 07 25 20 30  Message D     2009 07 25 21 08  Message E    2009 07 25 20 01  Message F     2009 07 25 20 17  Message G    2009 07 25 19 54  Message R

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Assuming your array contains strings  you can use the following   String   data   new String           2009 07 25 20 24 Message A        2009 07 25 20 17 Message G        2009 07 25 20 25 Message B        2009 07 25 20 30 Message D        2009 07 25 20 01 Message F        2009 07 25 21 08 Message E        2009 07 25 19 54 Message R      Arrays sort data  new Comparator lt String gt           Override     public int compare String s1  String s2            String t1   s1 substring 0  16      date time of s1         String t2   s2 substring 0  16      date time of s2         return t1 compareTo t2               If you have a two-dimensional array  the solution is also very similar   String     data   new String                   2009 07 25 20 17    Message G                2009 07 25 20 25    Message B                2009 07 25 20 30    Message D                2009 07 25 20 01    Message F                2009 07 25 21 08    Message E                2009 07 25 19 54    Message R        Arrays sort data  new Comparator lt String   gt           Override     public int compare String   s1  String   s2            String t1   s1 0           String t2   s2 0           return t1 compareTo t2

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If you are looking for easy one liners to sort 2d array  then here you go   Sort String     arr in ascending order by first column Arrays sort arr   a  b  - gt  a 0  compareTo b 0      Sort String     arr in descending order by first column Arrays sort arr   a  b  - gt  b 0  compareTo a 0      Sort String     arr in ascending order by second column Arrays sort arr   a  b  - gt  a 1  compareTo b 1      Sort String     arr in descending order by second column Arrays sort arr   a  b  - gt  b 1  compareTo a 1      Sort int     arr in ascending order by first column Arrays sort arr   a  b  - gt  Integer compare a 0   b 0      or Arrays sort arr   a  b  - gt  a 0  - b 0      Sort int     arr in descending order by first column Arrays sort arr   a  b  - gt  Integer compare b 0   a 0      or Arrays sort arr   a  b  - gt  b 0  - a 0      Sort int     arr in ascending order by second column Arrays sort arr   a  b  - gt  Integer compare a 1   b 1      or Arrays sort arr   a  b  - gt  a 1  - b 1      Sort int     arr in descending order by second column Arrays sort arr   a  b  - gt  Integer compare b 1   a 1      or Arrays sort arr   a  b  - gt  b 1  - a 1

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Arrays sort yourarray  new Comparator         public int compare Object o1  Object o2            String   elt1    String   o1          String   elt2    String   o2          return elt1 0  compareTo elt2 0

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Check out the ColumnComparator  It is basically the same solution as proposed by Costi  but it also supports sorting on columns in a List and has a few more sort properties

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install java8 jdk jre use lamda expression to sort 2D array    code   import java util Arrays  import java util Comparator   class SortString        public static void main final String   args            final String     data   new String                       new String      2009 07 25 20 24    Message A                     new String      2009 07 25 20 17    Message G                     new String      2009 07 25 20 25    Message B                     new String      2009 07 25 20 30    Message D                     new String      2009 07 25 20 01    Message F                     new String      2009 07 25 21 08    Message E                     new String      2009 07 25 19 54    Message R                           this is applicable only in java 8 version          Arrays sort data   String   s1  String   s2  - gt  s1 0  compareTo s2 0                 we can also use Comparator comparing and point to Comparable value we want to use                    Arrays sort data  Comparator comparing row- gt row 0              for  final String   s   data                System out println s 0          s 1                        output  2009 07 25 19 54 Message R 2009 07 25 20 01 Message F 2009 07 25 20 17 Message G 2009 07 25 20 24 Message A 2009 07 25 20 25 Message B 2009 07 25 20 30 Message D 2009 07 25 21 08 Message E

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class ArrayComparator implements Comparator lt Comparable   gt        private final int columnToSort      private final boolean ascending       public ArrayComparator int columnToSort  boolean ascending            this columnToSort   columnToSort          this ascending   ascending             public int compare Comparable   c1  Comparable   c2            int cmp   c1 columnToSort  compareTo c2 columnToSort            return ascending   cmp   -cmp            This way you can handle any type of data in those arrays  as long as they re Comparable  and you can sort any column in ascending or descending order   String     data   getData    Arrays sort data  new ArrayComparator 0  true      PS  make sure you check for ArrayIndexOutOfBounds and others   EDIT  The above solution would only be helpful if you are able to actually store a java util Date in the first column or if your date format allows you to use plain String comparison for those values  Otherwise  you need to convert that String to a Date  and you can achieve that using a callback interface  as a general solution   Here s an enhanced version   class ArrayComparator implements Comparator lt Object   gt        private static Converter DEFAULT CONVERTER   new Converter              Override         public Comparable convert Object o                   simply assume the object is Comparable             return  Comparable  o                       private final int columnToSort      private final boolean ascending      private final Converter converter        public ArrayComparator int columnToSort  boolean ascending            this columnToSort  ascending  DEFAULT CONVERTER              public ArrayComparator int columnToSort  boolean ascending  Converter converter            this columnToSort   columnToSort          this ascending   ascending          this converter   converter             public int compare Object   o1  Object   o2            Comparable c1   converter convert o1 columnToSort            Comparable c2   converter convert o2 columnToSort            int cmp   c1 compareTo c2           return ascending   cmp   -cmp            interface Converter       Comparable convert Object o      class DateConverter implements Converter       private static final DateFormat df   new SimpleDateFormat  yyyy MM dd hh mm          Override     public Comparable convert Object o            try               return df parse o toString               catch  ParseException e                throw new IllegalArgumentException e                       And at this point  you can sort on your first column with   Arrays sort data  new ArrayComparator 0  true  new DateConverter       I skipped the checks for nulls and other error handling issues   I agree this is starting to look like a framework already      Last  hopefully  edit  I only now realize that your date format allows you to use plain String comparison  If that is the case  you don t need the  enhanced version

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Sort a two dimensional array based on one column   The first column is a date of format  yyyy MM dd HH mm  and the second column is a String    Since you say 2-D array  I assume  date of format      means a String  Here s code for sorting a 2-D array of String       import java util Arrays  import java util Comparator   public class Asdf        public static void main final String   args            final String     data   new String                       new String      2009 07 25 20 24    Message A                     new String      2009 07 25 20 17    Message G                     new String      2009 07 25 20 25    Message B                     new String      2009 07 25 20 30    Message D                     new String      2009 07 25 20 01    Message F                     new String      2009 07 25 21 08    Message E                     new String      2009 07 25 19 54    Message R                Arrays sort data  new Comparator lt String   gt                   Override             public int compare final String   entry1  final String   entry2                    final String time1   entry1 0                   final String time2   entry2 0                   return time1 compareTo time2                                      for  final String   s   data                System out println s 0          s 1                         Output   2009 07 25 19 54 Message R 2009 07 25 20 01 Message F 2009 07 25 20 17 Message G 2009 07 25 20 24 Message A 2009 07 25 20 25 Message B 2009 07 25 20 30 Message D 2009 07 25 21 08 Message E

[java] Sort a two dimensional array based on one column

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