CS321 Chapter 4

In Java every class must have a name. Anonymous classes are not allowed.

False

Polymorphism means that different methods are selected according to the interface or actual object type whichever is more consistent with the programmer's intentions.

False

When an overridden method is called through a superclass reference, Java determines which version(superclass/subclasses) of that method is to be executed based upon the type of the object being referred to at the time the code is compiled.

False

A JFrame can be used to display content in what is commonly called a window.

True

A JOptionPane can be used to display messages to the user.

True

An instance of the Timer class in the javax.swing package can be used for simple animation.

True

Components such as JButton or JTextPane can be added to a JFrame.

True

If a class declares that it implements an interface and does not implement all of the methods of the interface, then the class must be declared abstract.

True

In Java, actionPerformed is the method in the ActionListener class that must be implemented for a JButton to respond to a mouse click.

True

In Java, there is no need to create a subclass for the Icon interface. The programmer only needs to implement the contracted methods.

True

In a correct Java program, a variable can be of either an interface type or a class type.

True

Multiple classes can implement the same interface type but a class can extend only one superclass.

True

Runtime polymorphism is also known as dynamic method dispatch and it is a process in which a function call to the overridden method is resolved at runtime

True

Until Java 8, interfaces could contain no implementations. As of Java 8 default implementations are allowed.

True