Adding null values to arraylist

Question

Can I add null values to an ArrayList even if it has a generic type parameter   Eg   ArrayList lt Item gt  itemList   new ArrayList lt Item gt     itemList add null     If so  will  itemsList size      return 1 or 0   If I can add null values to an ArrayList  can I loop through only the indexes that contain items like this   for Item i   itemList         code here     Or would the for each loop also loop through the null values in the list

User · Answer

You can add nulls to the ArrayList  and you will have to check for nulls in the loop   for Item i   itemList       if  i    null              itemsList size    would take the null into account    List lt Integer gt  list   new ArrayList lt Integer gt      list add null    list add  5    System out println  list size      for  Integer value   list       if  value    null         System out println   null value       else         System out println  value        Output     2 null value 5

User · Answer

You could create Util class  public final class CollectionHelpers       public static  lt T gt  boolean addNullSafe List lt T gt  list  T element            if  list    null    element    null                return false                     return list add element            And then use it  Element element   getElementFromSomeWhere someParameter   List lt Element gt  arrayList   new ArrayList lt  gt     CollectionHelpers addNullSafe list  element

User · Answer

Yes  you can always use null instead of an object  Just be careful because some methods might throw error   It would be 1   also nulls would be factored in in the for loop  but you could use   for Item i   itemList            if  i   null                     code here

[java] Adding null values to arraylist

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