How to use subList

Question

I have a JSF page which displays list of Glassfish log files  I use lazy loading for pagination  I keep the list of the log files names into Java List   private List lt directoryListObj gt  dataList   new ArrayList lt  gt      dataList   dataList subList firstRow  lastRow     And here is the problem  For example I have 35 files into the directory  When I do this   dataList   dataList subList 5  15     It works fine  But when I do this   dataList   dataList subList 30  38     I get error wrong index because I want to get index outside of the List  How I can for example return List elements from 30 to 35  I want if I want to get index from 30 to 40 but if there only 35 indexes to get only 5

User · Answer

You could use streams in Java 8  To always get 10 entries at the most  you could do   dataList stream   skip 5  limit 10  collect Collectors toList     dataList stream   skip 30  limit 10  collect Collectors toList

User · Answer

I ve implemented and tested this one  it should cover most bases   public static  lt T gt  List lt T gt  safeSubList List lt T gt  list  int fromIndex  int toIndex        int size   list size        if  fromIndex  gt   size    toIndex  lt   0    fromIndex  gt   toIndex            return Collections emptyList               fromIndex   Math max 0  fromIndex       toIndex   Math min size  toIndex        return list subList fromIndex  toIndex

User · Answer

To get the last element  simply use the size of the list as the second parameter  So for example  if you have 35 files  and you want the last five  you would do   dataList subList 30  35     A guaranteed safe way to do this is   dataList subList Math max 0  first   Math min dataList size    last

User · Answer

Using subList 30  38   will fail because max index 38 is not available in list  so its not possible   Only way may be before asking for the sublist  you explicitly determine the max index using list size   method   for example  check size  which returns 35  so call sublist 30  size      OR   COPIED FROM pb2q comment  dataList   dataList subList 30  38  gt  dataList size     dataList size     38

[java] How to use subList()

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