Wrapper classes and ArrayList: methods and traversal

Learning objectives

Explain that Integer and Double are immutable wrapper classes holding an int or a double as an object, and identify where Java autoboxes a primitive and unboxes a wrapper automatically

Convert a String to a number with Integer.parseInt and Double.parseDouble, and explain why an ArrayList of numbers is declared with Integer or Double rather than int or double

Declare and create an ArrayList with a type parameter, and use size, add, get, set and remove, stating what each returns and how the index forms of add and remove shift the other elements

Traverse an ArrayList with an indexed for loop, a while loop and an enhanced for loop, and explain why removing elements in a forward indexed loop can skip an element

Explain the ConcurrentModificationException raised when an ArrayList changes size during an enhanced for loop, and the IndexOutOfBoundsException raised by an invalid index

Compare an array with an ArrayList on fixed or changing size, on the syntax for reading and writing elements and on the storage of primitive values