Objects: classes, instantiation and calling instance methods

Learning objectives

Distinguish a class, the blueprint that defines attributes and behaviors, from an object, one instance of it, and explain that a reference variable stores the location of an object rather than the object itself

Describe how a superclass gathers the attributes and behaviors shared by related subclasses, and state that every Java class is a subclass of the Object class

Create objects with the keyword new and a constructor call, choosing between overloaded constructors by the number, order and types of the arguments supplied

Call instance methods with the dot operator, passing arguments that match each parameter list, and use the value returned by a non-void method inside a larger expression

Explain the meaning of null, and predict the NullPointerException raised when an instance method is called through a reference that holds null

Read the documentation of an unfamiliar class and write code that constructs an object of it and calls its methods correctly