How do I sort a Set to a List in Java

Question

In Java  I have a Set  and I want to turn it into a sorted List   Is there a method in the java util Collections package that will do this for me

User · Answer

TreeSet sortedset   new TreeSet    sortedset addAll originalset    list addAll sortedset     where originalset   unsorted set and list   the list to be returned

User · Answer

There s no single method to do that   Use this    SuppressWarnings  unchecked   public static  lt T extends Comparable gt  List lt T gt  asSortedList Collection lt T gt  collection      T   array   collection toArray       T   new Comparable collection size        Arrays sort array     return Arrays asList array

User · Answer

Sorted set      return new TreeSet setIWantSorted     or   return new ArrayList new TreeSet setIWantSorted

User · Answer

Always safe to use either Comparator or Comparable interface to provide sorting implementation  if the object is not a String or Wrapper classes for primitive data types     As an example for a comparator implementation to sort employees based on name      List lt Employees gt  empList   new LinkedList lt Employees gt  EmpSet        class EmployeeComparator implements Comparator lt Employee gt                 public int compare Employee e1  Employee e2                    return e1 getName   compareTo e2 getName                                  Collections sort empList   new EmployeeComparator        Comparator is useful when you need to have different sorting algorithm on same object  Say emp name  emp salary  etc   Single mode sorting can be implemented by using Comparable interface in to the required object

User · Answer

Jeremy Stein I wanted to implement same code  As well I wanted to sort the set to list  So instead of using Set I converted set values into List and sort that list by it s one the variable  This code helped me   set stream   sorted Comparator comparing ModelClassName  sortingVariableName   collect Collectors toList

User · Answer

The answer provided by the OP is not the best  It is inefficient  as it creates a new List and an unnecessary new array  Also  it raises  unchecked  warnings because of the type safety issues around generic arrays   Instead  use something like this    public static  lt T extends Comparable lt   super T gt  gt  List lt T gt  asSortedList Collection lt T gt  c      List lt T gt  list   new ArrayList lt T gt  c     java util Collections sort list     return list      Here s a usage example   Map lt Integer  String gt  map   new HashMap lt Integer  String gt        Add entries to the map            Now get a sorted list of the  values  in the map     Collection lt String gt  unsorted   map values    List lt String gt  sorted   Util asSortedList unsorted

User · Answer

Here s how you can do it with Java 8 s Streams   mySet stream   sorted   collect Collectors toList       or with a custom comparator   mySet stream   sorted myComparator  collect Collectors toList

User · Answer

I am using this code  which I find more practical than the accepted answer above   List lt Thing gt  thingList   new ArrayList lt  gt  thingSet   thingList sort  thing1  thing2  - gt  thing1 getName   compareToIgnoreCase thing2 getName

User · Answer

List myList   new ArrayList collection   Collections sort myList         should do the trick however  Add flavour with Generics where applicable

User · Answer

You can convert a set into an ArrayList  where you can sort the ArrayList using Collections sort List    Here is the code   keySet    Set  map keySet    ArrayList list   new ArrayList keySet        Collections sort list

[java] How do I sort a Set to a List in Java?

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