How to sort a List Object alphabetically using Object name field

Question

I have a List of Objects like List lt Object gt  p I want to sort this list alphabetically using Object name field  Object contains 10 field and name field is one of them   if  list size    gt  0        Collections sort list  new Comparator lt Campaign gt               Override         public int compare final Object object1  final Object object2            return String compare object1 getName    object2 getName                            But there is nothing like String compare

User · Accepted Answer

From your code  it looks like your Comparator is already parameterized with Campaign  This will only work with List lt Campaign gt   Also  the method you re looking for is compareTo    if  list size    gt  0      Collections sort list  new Comparator lt Campaign gt             Override       public int compare final Campaign object1  final Campaign object2              return object1 getName   compareTo object2 getName                       Or if you are using Java 1 8  list    stream      sorted  object1  object2  - gt  object1 getName   compareTo object2 getName        One final comment -- there s no point in checking the list size  Sort will work on an empty list

User · Answer

Here is a version of Robert B s answer that works for List lt T gt  and sorting by a specified String property of the object using Reflection and no 3rd party libraries         Sorts a List by the specified String property name of the object          param list     param propertyName     public static  lt T gt  void sortList List lt T gt  list  final String propertyName         if  list size    gt  0            Collections sort list  new Comparator lt T gt                   Override             public int compare final T object1  final T object2                    String property1    String ReflectionUtils getSpecifiedFieldValue  propertyName  object1                   String property2    String ReflectionUtils getSpecifiedFieldValue  propertyName  object2                   return property1 compareToIgnoreCase  property2                                       public static Object getSpecifiedFieldValue  String property  Object obj         Object result   null       try           Class lt   gt  objectClass   obj getClass            Field objectField   getDeclaredField property  objectClass           if  objectField  null                objectField setAccessible true               result   objectField get obj                   catch  Exception e                       return result     public static Field getDeclaredField String fieldName  Class lt   gt  type         Field result   null      try           result   type getDeclaredField fieldName         catch  Exception e                      if  result    null            Class lt   gt  superclass   type getSuperclass                 if  superclass    null  amp  amp   superclass getName   equals  java lang Object                         return getDeclaredField fieldName  type getSuperclass                         return result

User · Answer

Using a selection Sort  for int i   list size   - 1  i  gt  0  i--      int max   i    for int j   0  j  lt  i  j           if list get j  getName   compareTo list get j  getName     gt  0               max  j                   make the swap   Object temp   list get i     list get i    list get max     list get max    temp

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Victor s answer worked for me and reposting it here in Kotlin in case useful to someone else doing Android  if  list   isNotEmpty         Collections sort       list       Comparator   c1  c2 - gt    You should ensure that list doesn t contain null values       c1 name   compareTo c2 name

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You can use sortThisBy   from Eclipse Collections   MutableList lt Campaign gt  list   Lists mutable empty    list sortThisBy Campaign  getName     If you can t change the type of list from List   List lt Campaign gt  list   new ArrayList lt  gt     ListAdapter adapt list  sortThisBy Campaign  getName     Note  I am a contributor to Eclipse Collections

User · Answer

if listAxu size    gt  0        Collections sort listAxu  new Comparator lt Situacao gt              Override         public int compare Situacao lhs  Situacao rhs                            return lhs getDescricao   compareTo rhs getDescricao

User · Answer

This is assuming a list of YourClass instead of Object  as explained by amit   You can use this bit from the Google Guava library   Collections sort list  Ordering natural      onResultOf new Function lt String YourClass gt        public String call YourClass o         return o getName             nullsLast      The other answers which mention Comparator are not incorrect  since Ordering implements Comparator  This solution is  in my opinion  a little easier  though it may be harder if you re a beginner and not used to using libraries and or  functional programming    Copied shamelessly from this answer on my own question

User · Answer

The most correct way to sort alphabetically strings is to use Collator  because of internationalization  Some languages have different order due to few extra characters etc      Collator collator   Collator getInstance Locale US      if   list isEmpty          Collections sort list  new Comparator lt Campaign gt               Override         public int compare Campaign c1  Campaign c2                  You should ensure that list doesn t contain null values              return collator compare c1 getName    c2 getName                                 If you don t care about internationalization use string compare otherString       if   list isEmpty          Collections sort list  new Comparator lt Campaign gt               Override         public int compare Campaign c1  Campaign c2                  You should ensure that list doesn t contain null values              return c1 getName   compare c2 getName

User · Answer

Try this   List lt  Object gt  myList   x getName  myList sort Comparator comparing Object  getName

User · Answer

If your objects has some common ancestor  let it be T  you should use List lt T gt  instead of List lt Object gt   and implement a Comparator for this T  using the name field    If you don t have a common ancestor  you can implement a Comperator  and use reflection to extract the name  Note that it is unsafe  unsuggested  and suffers from bad performance to use reflection  but it allows you to access a field name without knowing anything about the actual type of the object  besides the fact that it has a field with the relevant name   In both cases  you should use Collections sort   to sort

User · Answer

something like    List lt FancyObject gt  theList           Collections sort  theList                      new Comparator lt FancyObject gt                           int compare  final FancyObject a  final FancyObject d                              return  a getName   compareTo d getName

User · Answer

Using Java 8 Comparator comparing   list sort Comparator comparing Campaign  getName

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If you are using a List lt Object gt  to hold objects of a subtype that has a name field  lets call the subtype NamedObject   you ll need to downcast the list elements in order to access the name   You have 3 options  the best of which is the first    Don t use a List lt Object gt  in the first place if you can help it - keep your named objects in a List lt NamedObject gt  Copy your List lt Object gt  elements into a List lt NamedObject gt   downcasting in the process  do the sort  then copy them back Do the downcasting in the Comparator   Option 3 would look like this   Collections sort p  new Comparator lt Object gt               int compare  final Object a  final Object b                    return   NamedObject  a  getName   compareTo  NamedObject b  getName

User · Answer

Have a look at Collections sort   and the Comparator interface   String comparison can be done with object1 getName   compareTo object2 getName    or object2 getName   compareTo object1 getName     depending on the sort direction you desire    If you want the sort to be case agnostic  do object1 getName   toUpperCase   compareTo object2 getName   toUpperCase

User · Answer

public class ObjectComparator implements Comparator lt Object gt         public int compare Object obj1  Object obj2            return obj1 getName   compareTo obj2 getName                Please replace Object with your class which contains name field  Usage   ObjectComparator comparator   new ObjectComparator    Collections sort list  comparator

User · Answer

I found another way to do the type   if listAxu size    gt  0       Collections sort listAxu  Comparator comparing IdentityNamed  getDescricao

[java] How to sort a List<Object> alphabetically using Object name field

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