final.txt

java tutorial.sun公司官方出品。java入门书籍。最新版

Questions
---------
1. The program Problem.java doesn't compile.  What do you need to do
   to make it compile?  Why?
   [.../tutorial/java/javaOO/QandE-1dot1/Problem.java]
ANSWER: Add "final" in front of the declaration of the <code>timer</code>
	variable.  As it says in "Other Facts about Nested Classes",
	"A nested class declared within a method...has access to any
	final, local variables in scope."

2. Use the 1.3 API documentation for the Box class (in the
   javax.swing package) to help you answer the following questions.

   a. What static nested class does Box define?
ANSWER: Box.Filler

   b. What inner class does Box define?
ANSWER: Box.AccessibleBox   

   c. What is the superclass of Box's inner class?
ANSWER: [java.awt.]Container.AccessibleAWTContainer
  
   d. Which of Box's nested classes can you use from any class?
ANSWER: Box.Filler

   e. How do you create an instance of Box's Filler class?
ANSWER: 
	new Box.Filler(minDimension, prefDimension, maxDimension)

3. What kind of nested class is most appropriate for each of the following
   situations?  [PENDING: can we make that clearer?  Is there a term
   for this kind of one-to-one matching question?]

   a. The only users of this nested class will be instances of
      the enclosing class or instances of the enclosing class's
      subclasses.
ANSWER: B

   b. Anyone can use this nested class.
ANSWER: C

   c. Only instances of the declaring class need to use this nested
      class, and a particular instance might use it several times.
ANSWER: F

   d. This tiny nested class is used just once, to create an
      object that implements an interface.
ANSWER: A

   e. This nested class has information about its enclosing class
      (not about instances of the enclosing class) and is used
      only by its enclosing class and perhaps their subclasses.
ANSWER: D

   f. Like e, but not intended to be used by subclasses.
ANSWER: E

   A. anonymous inner class
   B. protected inner class
   C. public static nested class
   D. protected static nested class
   E. private static nested class
   F. private inner class


Exercises
---------
1. First, get the source file InnerClassDemo.java.  
   [.../tutorial/java/javaOO/QandE-1dot2/InnerClassDemo.java]

   a. Compile and run InnerClassDemo.  If you have problems, see
      Compiling and Running Swing Programs
      [http://java.sun.com/docs/books/tutorial/uiswing/start/swingStart.html].
   
ANSWER: N/A. [This step is here just to make sure they can compile
	and run Swing programs, before they start trying to change
	the programs.]

   b. Make a copy of InnerClassDemo.  Add to it an inner class named
      MyActionListener that implements the ActionListener interface
   [http://java.sun.com/products/jdk/1.3/docs/api/java/awt/event/ActionListener.html].
      The ActionListener interface defines a single method.  Put the
      following code into your implementation of the method:
   
         quit();

      Delete the "//" in front of the following line of code:

	 //button.addActionListener(new MyActionListener());

      Now compile and run the program.  What is the difference in
      behavior between this version and the previous version of
      InnerClassDemo?

ANSWER: See InnerClassDemo2.java
   [.../tutorial/java/javaOO/QandE-1dot2/InnerClassDemo2.java]
	In this version, the button actually *does* something
	(makes the program exit).

   c. Make a copy of the program you created for b.  Change your
      ActionListener implementation to be an anonymous inner class.
      Hint: The program already has another anonymous inner class
      (a WindowAdapter), which you can look at for syntax help.

ANSWER: See InnerClassDemo3.java
   [.../tutorial/java/javaOO/QandE-1dot2/InnerClassDemo3.java]

2. Get the file Class1.java
   [.../tutorial/java/javaOO/QandE-1dot1/Class1.java].
  
   a. Compile and run Class1.  What is the output?
ANSWER: 
      InnerClass1: getString invoked.
      InnerClass1: getAnotherString invoked.

   b. Create a file called Class2.java that defines subclasses
      of both Class1 and its inner class, InnerClass1.  (Call the
      subclasses Class2 and InnerClass2, respectively.)  InnerClass2
      should override the getAnotherString method to return 
      "InnerClass2 version of getAnotherString invoked".  

      Class2 should define one constructor and one method:

      - A no-argument constructor that initializes the inherited
	<code>ic</code>
        instance variable to be an instance of InnerClass2.
      - A <code>main</code> method that creates an instance 
         of Class2 and invokes displayStrings on that instance.

      What is the output when you run Class2?
ANSWER: 
      InnerClass1: getString invoked.
      InnerClass2 version of getAnother String invoked.
See Class2.java
   [.../tutorial/java/javaOO/QandE-1dot1/Class2.java]