• List and its supporting classes (such as ArrayList) can be used to manipulate lists of objects of any classes.
• We can have a list of strings, a list of people, a list of shapes, ...
• This is possible because the interface and the classes are written in terms of the class Object.
• It is possible to add objects of many different classes to a list.
• Most of the time we will not want to do this.
• If we do it inadvertently, this error will not be detected at compilation time as what we have written is allowed.