0: Amy 1: Bob 2: Deb
isEmpty()
To check if an ArrayList
has elements use
boolean isEmpty()
which returns true
if the cells of the ArrayList
are all empty.
Warning:The value null
in a cell counts as data.
An empty cell is not the same as a cell that contains null
.
To remove all elements from a list, use
void clear()
(Puzzle: ) What will the following program print?
import java.util.* ; public class NullPuzzle { public static void main ( String[] args) { ArrayList<String> nobby = new ArrayList<String>(); System.out.println( "Case A:" + nobby.isEmpty() ); nobby.add( null ); System.out.println( "Case B:" + nobby.isEmpty() ); nobby.remove( 0 ); System.out.println( "Case C:" + nobby.isEmpty() ); nobby.add( "" ); System.out.println( "Case D:" + nobby.isEmpty() ); nobby.clear( ); System.out.println( "Case E:" + nobby.isEmpty() ); } }