How to copy java util list Collection

Question

I am implementing a Java class responsible for ordering java util List  The problem comes when I use this class  I m able to ordering the list but I want to copy the  original  list without modification so that I could register every change made on the original list  The sorted list contains object and one of its fields stores a classification id  and this id it is updated with the index value of the list   I tried to use clone method and it keeps the list unsorted but the changes made on original list are updated in the clone list too   Is there any way to accomplish it   My Code   List lt Torero gt  listaTorero   tbTlgTorerolHome findByExample new Torero     List lt Torero gt  listaToreroTemp     List lt Torero gt     ArrayList lt Torero gt   listaTorero  clone       Clasificacion clasificacion   new Clasificacion     Iterator lt Torero gt  iterTorero   clasificacion getClasificacion listaTorero  torero  iterator      Sorting List   A Clasificacion method   public List lt Torero gt  getClasificacion List lt Torero gt  listaToreroTemp  Torero torero         List lt Torero gt  listaTorero   new ArrayList lt Torero gt          Collections sort listaToreroTemp new ToreroClasifiacionComparator          Iterator lt Torero gt  iterTorero   listaToreroTemp iterator        int index 1      while iterTorero hasNext                  Torero toreroTemp   iterTorero next            toreroTemp setNumClasificacion index           listaTorero add toreroTemp           index index 1            return listaTorero

User · Answer

Use the ArrayList copy constructor  then sort that   List oldList  List newList   new ArrayList oldList   Collections sort newList     After making the copy  any changes to newList do not affect oldList   Note however that only the references are copied  so the two lists share the same objects  so changes made to elements of one list affect the elements of the other

User · Answer

You may create a new list with an input of a previous list like so   List one   new ArrayList         add data  sort  etc List two   new ArrayList one     This will allow you to modify the order or what elemtents are contained independent of the first list   Keep in mind that the two lists will contain the same objects though  so if you modify an object in List two  the same object will be modified in list one   example   MyObject value1   one get 0   MyObject value2   two get 0   value1    value2   true value1 setName  hello    value2 getName      returns  hello    Edit  To avoid this you need a deep copy of each element in the list like so   List lt Torero gt  one   new ArrayList lt Torero gt       add elements  List lt Torero gt  two   new Arraylist lt Torero gt     for Torero t   one       Torero copy   deepCopy t       two add copy       with copy like the following   public Torero deepCopy Torero input       Torero copy   new Torero        copy setValue input getValue         copy primitives  deep copy objects again      return copy

[java] How to copy java.util.list Collection

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