How to sort a List of objects by their date java collections List Object

Question

private List lt Movie gt  movieItems   null  public List lt Movie gt  getMovieItems         final int first   0      if  movieItems    null            getPagingInfo            movieItems   jpaController findRange new int   pagingInfo getFirstItem    pagingInfo getFirstItem     pagingInfo getBatchSize              Collections sort movieItems  new Comparator               public int compare  Object o1  Object o2                  Date d1   movieItems get   Movie o1  getMovieId    getDate                   Date d2   movieItems get   Movie o2  getMovieId    getDate                   if d1 before d2                       movieItems set 1   Movie o1                      movieItems set 2   Movie o2                                   return first                                    return movieItems      jpaController is bringing back 4 movies and is giving me the following     java lang ArrayIndexOutOfBoundsException  Array index out of range  4     at java util Vector get Vector java 694     at   entitybeans jsf PeliculaController 1 compare PeliculaController java 260      at java util Arrays mergeSort Arrays java 1270      at   java util Arrays sort Arrays java 1210    at   java util Collections sort Collections java 159   at   entitybeans jsf PeliculaController getPeliculaItems PeliculaController java 257      at sun reflect NativeMethodAccessorImpl invoke0 Native Method   at   sun reflect NativeMethodAccessorImpl invoke NativeMethodAccessorImpl java 39      at   sun reflect DelegatingMethodAccessorImpl invoke DelegatingMethodAccessorImpl java 25      at java lang reflect Method invoke Method java 597      at   javax el BeanELResolver getValue BeanELResolver java 302      at   javax el CompositeELResolver getValue CompositeELResolver java 175      at   com sun faces el FacesCompositeELResolver getValue FacesCompositeELResolver java 72      at com sun el parser AstValue getValue AstValue java 116    at   com sun el parser AstValue getValue AstValue java 163

User · Answer

I d add Commons NullComparator instead to avoid some problems

User · Answer

In Java 8  it s now as simple as   movieItems sort Comparator comparing Movie  getDate

User · Answer

You can use this   Collections sort list  org joda time DateTimeComparator getInstance

User · Answer

You re using Comparators incorrectly    Collections sort movieItems  new Comparator lt Movie gt                public int compare  Movie m1  Movie m2                  return m1 getDate   compareTo m2 getDate

User · Answer

In your compare method  o1 and o2 are already elements in the movieItems list  So  you should do something like this   Collections sort movieItems  new Comparator lt Movie gt          public int compare Movie m1  Movie m2            return m1 getDate   compareTo m2 getDate

User · Answer

Do not access or modify the collection in the Comparator  The comparator should be used only to determine which object is comes before another  The two objects that are to be compared are supplied as arguments   Date itself is comparable  so  using generics   class MovieComparator implements Comparator lt Movie gt        public int compare Movie m1  Movie m2             possibly check for nulls to avoid NullPointerException        return m1 getDate   compareTo m2 getDate               And do not instantiate the comparator on each sort  Use   private static final MovieComparator comparator   new MovieComparator

[java] How to sort a List of objects by their date (java collections, List<Object>)

Examples related to java

Examples related to sorting

Examples related to collections