I am trying to create a new array in this way:
final boolean[] arr = new boolean[list.size()];
This line is throwing a null pointer in my code in some cases. Under what situations can this happen? Can it happen when the list has zero elements? I am sure the list is not null at this stage.
Having a NullPointerException thrown, means you have an uninitialized object. It has nothing to do with anything else. If the exception is thrown out of the line you mentioned, then as the comments on your question says, your list hasn't been initialized.
To create an array using a dynamic length (Note that an array size CANNOT change after is has been initialized), you can do this:
ArrayList<String> list = new ArrayList<String>();
//Add elements to your list
String[] arr = list.toArray(new String[list.size()]);
This can only happen, if list is null.
If list is empty, list.size() will return 0.
boolean[] arr = new boolean[0];
Even it is a valid syntax. you can create array with 0 size. So untill and unless list null it will not produce NullPointerException
The null point can occur when list is null, if it's only occurring on that line. If that is the exception you're getting, then list is null. Have another look at your code, and I'm sure you'll find out. Alternatively, debug your code and check the value of list at this line.
list was never instantiated. So, it is null. Check if you instantiated the list after declaration.
Please use List instead of array and finally get the array from the list ..
Make sure you have initialized your list variable. The only way it will throw a NPE is due to the list itself being null.
