Review Questions - For Revisions
What is the difference between static and non-static variables?
A static variable is associated with the class as a whole rather than
with specific instances of a class. Non-static variables take on unique
values with each object instance.
What is the difference between the paint() and repaint() methods?
The paint() method supports painting via a Graphics object. The repaint()
method is used to cause paint() to be invoked by the AWT painting thread.
What is the purpose of the File class?
The File class is used to create objects that provide access to the
files and directories of a local file system.
Can an exception be rethrown?
Yes, an exception can be rethrown.
Which Math method is used to calculate the absolute value of a number?
The abs() method is used to calculate absolute values.
How does multithreading take place on a computer with a single CPU?
The operating system's task scheduler allocates execution time to multiple
tasks. By quickly switching between executing tasks, it creates the impression
that tasks execute sequentially.
When does the compiler supply a default constructor for a class?
The compiler supplies a default constructor for a class if no other
constructors are provided.
When is the finally clause of a try-catch-finally statement executed?
The finally clause of the try-catch-finally statement is always executed
unless the thread of execution terminates or an exception occurs within
the execution of the finally clause.
Which class is the immediate superclass of the Container class?
If a method is declared as protected, where may the method be accessed?
A protected method may only be accessed by classes or interfaces of
the same package or by subclasses of the class in which it is declared.
How can the Checkbox class be used to create a radio button?
By associating Checkbox objects with a CheckboxGroup.
Which non-Unicode letter characters may be used as the first character
of an identifier?
The non-Unicode letter characters $ and _ may appear as the first character
of an identifier
What restrictions are placed on method overloading?
Two methods may not have the same name and argument list but different
What happens when you invoke a thread's interrupt method while it
is sleeping or waiting?
When a task's interrupt() method is executed, the task enters the ready
state. The next time the task enters the running state, an InterruptedException
What is casting?
There are two types of casting, casting between primitive numeric types
and casting between object references. Casting between numeric types is
used to convert larger values, such as double values, to smaller values,
such as byte values. Casting between object references is used to refer
to an object by a compatible class, interface, or array type reference.
What is the return type of a program's main() method?
A program's main() method has a void return type.
Name four Container classes.
Window, Frame, Dialog, FileDialog, Panel, Applet, or ScrollPane
What is the difference between a Choice and a List?
A Choice is displayed in a compact form that requires you to pull it
down to see the list of available choices. Only one item may be selected
from a Choice. A List may be displayed in such a way that several List
items are visible. A List supports the selection of one or more List items.
What class of exceptions are generated by the Java run-time system?
The Java runtime system generates RuntimeException and Error exceptions.
What class allows you to read objects directly from a stream?
The ObjectInputStream class supports the reading of objects from input
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