Java ArrayList - Check if list is empty

Question

How can I check if a list is empty  If so  the system has to give a message saying List is empty  If not  the system has to give a message saying List is not empty  Users can enter numbers  -1 to stop the program  This is the code I now have  but this doesn t work  it always says  List isn t empty    import java util    import javax swing JOptionPane   public class ArrayListEmpty        public static void main String   args                 List lt Integer gt  numbers   new ArrayList lt Integer gt             int number          do               number   Integer parseInt JOptionPane showInputDialog  Enter a number  -1 to stop                  numbers add number             while  number    -1           giveList numbers              public static void giveList List lt Integer gt  numbers                if  numbers    null              JOptionPane showMessageDialog null   List isn t empty            else             JOptionPane showMessageDialog null   List is empty

User · Answer

Source  CodeSpeedy Click to know more Check if an ArrayList is empty or not  import java util ArrayList  public class arraycheck   public static void main String args     ArrayList lt Integer gt  list new ArrayList lt Integer gt          if list size    0           System out println  Its Empty               else         System out println  Not Empty               Output   run  Its Empty BUILD SUCCESSFUL  total time  0 seconds

User · Answer

Good practice nowadays is to use CollectionUtils from either Apache Commons or Spring Framework   CollectionUtils isEmpty list

User · Answer

Your original problem was that you were checking if the list was null  which it would never be because you instantiated it with List lt Integer gt  numbers   new ArrayList lt Integer gt      However  you have updated your code to use the List isEmpty   method to properly check if the list is empty  The problem now is that you are never actually sending an empty list to giveList    In your do-while loop  you add any input number to the list  even if it is -1  To prevent -1 being added  change the do-while loop to only add numbers if they are not -1  Then  the list will be empty if the user s first input number is -1   do       number   Integer parseInt JOptionPane showInputDialog  Enter a number  -1 to stop             Change this line        if  number    -1  numbers add number     while  number    -1

User · Answer

As simply as   if  numbers isEmpty            Note that a quick look at the documentation would have given you that information

User · Answer

Alternatively  you may also want to check by the  size   method  The list that isn t empty will have a size more than zero  if  numbers size   gt 0     execute your code

User · Answer

You should use method listName isEmpty

[java] Java ArrayList - Check if list is empty

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