Add multiple items to already initialized arraylist in java

Question

I m googling it and can t seem to find the syntax  My arraylist might be populated differently based on a user setting  so I ve initialized it  ArrayList lt Integer gt  arList   new ArrayList lt Integer gt       And now I d like to add hundred of integers without doing it one by one with arList add 55

User · Answer

Collections addAll is a varargs method which allows us to add any number of items to a collection in a single statement   List lt Integer gt  list   new ArrayList lt  gt     Collections addAll list  1  2  3  4  5     It can also be used to add array elements to a collection   Integer   arr        Collections addAll list  arr

User · Answer

If you have another list that contains all the items you would like to add you can do arList addAll otherList   Alternatively  if you will always add the same elements to the list you could create a new list that is initialized to contain all your values and use the addAll   method  with something like   Integer   otherList   new Integer    1  2  3  4  5   arList addAll Arrays asList otherList      or  if you don t want to create that unnecessary array   arList addAll Arrays asList 1  2  3  4  5      Otherwise you will have to have some sort of loop that adds the values to the list individually

User · Answer

If you needed to add a lot of integers it d proabbly be easiest to use a for loop  For example  adding 28 days to a daysInFebruary array   ArrayList lt Integer gt  daysInFebruary   new ArrayList lt  gt      for int i   1  i  lt   28  i          daysInFebruary add i

User · Answer

I believe the answer above is incorrect  the proper way to initialize with multiple values would be this     int   otherList   1 2 3 4 5     so the full answer with the proper initialization would look like this  int   otherList   1 2 3 4 5   arList addAll Arrays asList otherList

User · Answer

If you are looking to avoid multiple code lines to save space  maybe this syntax could be useful            java util ArrayList lisFieldNames   new ArrayList                                   add  value1                     add  value2                               Removing new lines  you can show it compressed as            java util ArrayList lisFieldNames   new ArrayList                                   add  value1    add  value2

User · Answer

What is the  source  of those integer   If it is something that you need to hard code in your source code  you may do  arList addAll Arrays asList 1 1 2 3 5 8 13 21

[java] Add multiple items to already initialized arraylist in java

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