How can I sort a List alphabetically

Question

I have a List lt String gt  object that contains country names  How can I sort this list alphabetically

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Same in JAVA 8  -    Assecnding order         listOfCountryNames stream   sorted   forEach  x  - gt  System out println x       Decending order         listOfCountryNames stream   sorted  o1  o2  - gt  o2 compareTo o1   forEach  x  - gt  System out println x

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You can use the following line Collections sort listOfCountryNames  String CASE INSENSITIVE ORDER  It is similar to the suggestion of Thilo  but will not make a difference between upper and lowercase characters

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Here is what you are looking for  listOfCountryNames sort String  compareToIgnoreCase

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You can create a new sorted copy using Java 8 Stream or Guava      Java 8 version List lt String gt  sortedNames   names stream   sorted   collect Collectors toList        Guava version List lt String gt  sortedNames   Ordering natural   sortedCopy names      Another option is to sort in-place via Collections API   Collections sort names

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In one line  using Java 8    list sort Comparator naturalOrder

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Here is sorted List alphabetically with syncronized package com mnas technology automation utility  import java util ArrayList  import java util Collections  import java util Comparator  import java util Iterator  import java util List   import org apache log4j Logger            author manoj kumar    public class SynchronizedArrayList   static Logger log   Logger getLogger SynchronizedArrayList class getName      SuppressWarnings  unchecked   public static void main String   args     List lt Employee gt  synchronizedList   Collections synchronizedList new ArrayList lt Employee gt      synchronizedList add new Employee  Aditya     synchronizedList add new Employee  Siddharth     synchronizedList add new Employee  Manoj     Collections sort synchronizedList  new Comparator     public int compare Object synchronizedListOne  Object synchronizedListTwo      use instanceof to verify the references are indeed of the type in question return   Employee synchronizedListOne  name  compareTo   Employee synchronizedListTwo  name            for  Employee sd   synchronizedList    log info  Sorted Synchronized Array List     sd name           when iterating over a synchronized list  we need to synchronize access to the synchronized list synchronized  synchronizedList    Iterator lt Employee gt  iterator   synchronizedList iterator    while  iterator hasNext      log info  Sorted Synchronized Array List Items      iterator next   name            class Employee   String name  Employee  String name    this name   name

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Solution with Collections sort  If you are forced to use that List  or if your program has a structure like   Create List Add some country names sort them once never change that list again   then Thilos answer will be the best way to do it  If you combine it with the advice from Tom Hawtin - tackline  you get   java util Collections sort listOfCountryNames  Collator getInstance       Solution with a TreeSet  If you are free to decide  and if your application might get more complex  then you might change your code to use a TreeSet instead  This kind of collection sorts your entries just when they are inserted  No need to call sort     Collection lt String gt  countryNames        new TreeSet lt String gt  Collator getInstance     countryNames add  UK    countryNames add  Germany    countryNames add  Australia       Tada    sorted    Side note on why I prefer the TreeSet  This has some subtle  but important advantages    It s simply shorter  Only one line shorter  though  Never worry about is this list really sorted right now becaude a TreeSet is always sorted  no matter what you do  You cannot have duplicate entries  Depending on your situation this may be a pro or a con  If you need duplicates  stick to your List  An experienced programmer looks at TreeSet lt String gt  countyNames and instantly knows  this is a sorted collection of Strings without duplicates  and I can be sure that this is true at every moment  So much information in a short declaration  Real performance win in some cases  If you use a List  and insert values very often  and the list may be read between those insertions  then you have to sort the list after every insertion  The set does the same  but does it much faster    Using the right collection for the right task is a key to write short and bug free code  It s not as demonstrative in this case  because you just save one line  But I ve stopped counting how often I see someone using a List when they want to ensure there are no duplictes  and then build that functionality themselves  Or even worse  using two Lists when you really need a Map   Don t get me wrong  Using Collections sort is not an error or a flaw  But there are many cases when the TreeSet is much cleaner

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By using Collections sort    we can sort a list       public class EmployeeList        public static void main String   args               TODO Auto-generated method stub          List lt String gt  empNames  new ArrayList lt String gt              empNames add  sudheer            empNames add  kumar            empNames add  surendra            empNames add  kb             if  empNames isEmpty                  for String emp empNames                    System out println emp                              Collections sort empNames                System out println empNames                       output   sudheer kumar surendra kb  kb  kumar  sudheer  surendra

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Better late than never  Here is how we can do it for learning purpose only -  import java util List  import java util ArrayList  import java util Collections  import java util Comparator   class SoftDrink       String name      String color      int volume        SoftDrink  String name  String color  int volume            this name   name          this color   color          this volume   volume           public class ListItemComparision       public static void main  String   arg            List lt SoftDrink gt  softDrinkList   new ArrayList lt SoftDrink gt              softDrinkList  add new SoftDrink  Faygo    ColorOne   4            softDrinkList  add new SoftDrink  Fanta     ColorTwo   3            softDrinkList  add new SoftDrink  Frooti    ColorThree   2                   softDrinkList  add new SoftDrink  Freshie    ColorFour   1             Collections sort softDrinkList  new Comparator                  Override             public int compare Object softDrinkOne  Object softDrinkTwo                      use instanceof to verify the references are indeed of the type in question                 return   SoftDrink softDrinkOne  name                          compareTo   SoftDrink softDrinkTwo  name                                      for  SoftDrink sd   softDrinkList                System out println sd name     -     sd color     -     sd volume                     Collections sort softDrinkList  new Comparator                  Override             public int compare Object softDrinkOne  Object softDrinkTwo                      comparision for primitive int uses compareTo of the wrapper Integer                 return new Integer   SoftDrink softDrinkOne  volume                            compareTo   SoftDrink softDrinkTwo  volume                                      for  SoftDrink sd   softDrinkList                System out println sd volume     -     sd color     -     sd name

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Assuming that those are Strings  use the convenient static method sort      java util Collections sort listOfCountryNames

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descending alphabet   List lt String gt  list      Collections sort list   Collections reverse list

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Unless you are sorting strings in an accent-free English only  you probably want to use a Collator  It will correctly sort diacritical marks  can ignore case and other language-specific stuff   Collections sort countries  Collator getInstance new Locale languageCode       You can set the collator strength  see the javadoc   Here is an example for Slovak where    should go after S  but in UTF    is somewhere after Z   List lt String gt  countries   Arrays asList  Slovensko      v  dsko    Turecko     Collections sort countries   System out println countries      outputs  Slovensko  Turecko    v  dsko   Collections sort countries  Collator getInstance new Locale  sk      System out println countries      outputs  Slovensko    v  dsko  Turecko

User · Answer

Use the two argument for of Collections sort  You will want a suitable Comparator that treats case appropriate  i e  does lexical  not UTF16 ordering   such as that obtainable through java text Collator getInstance

[java] How can I sort a List alphabetically?

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