Exercise 2a. Finding a Class.
Technique 1
You could just scroll up and down the list but as there are more
than 100 entries a better technique is required.
- Click in the Class list pane, say on Object, and type in
the first letter or 2 of the required class, the list will
automatically start to home in.
- Start to search for Toad, and type t. Toad is
found straight away.
- Start another search by Clicking in the pane. Search
for ByteString by typing in by and ByteString is
found.
- Start another search by Clicking in the pane. Search
for Character.
- Type in c finds ClassDescription, continue
typing
- h finds CharTable, continue typing
- ara finds CharacterArray
- you can complete the typing but this technique fails
to find Character.
Exercise 2b. Finding a Class. Technique 2
- Click on the Find button and hold down the mouse button.
- Move over Class... and release.
- Read the text, note how we can use pattern matching.
- Type in c*
- Select Character from the list of about 8 classes.
- Click OK
- If you had typed in ch* or chara* etc. the list would
be shorter.
Exercise 3. Finding a Method
- Hold down the left mouse button with the pointer over the
Find button.
- Slide the pointer over Implementors of method...and
release.
- Type in the method name, including the : (colon)
if a keyword method.
- Click OK
- Search for the following. plus:, holder
- Note how you have a View window with a single class
in the upper pane, and the actual method in the lower
pane.
- Search for the following. at:put:
- Note how you have a View window with a multiple
classes in the upper pane, the method in the lower
pane displays the method for the selected class.
Exercise 4. Finding Examples
of a Method
This is useful to see how a method is used. You can find how the
method that you are interested in is used within other methods.
- Hold down the left mouse button with the pointer over the
Find button.
- Slide the pointer over References to method...and
release.
- Type in the method name, including the : (colon)
if a keyword method.
- Click OK
Exercise 5. Class
Hierarchy.
This can be seen in the Class pane. Object is at the top of the
list. All the other classes are indented.
- The first indentation shows the direct subclasses of Object.
E.g.
- Account
- Amphibian. Note you are using the Class browser
in LB-27. There was no Amphibian class before LB-21,
Frog and Toad classes were direct subclasses
of Object class earlier in the course hierarchy
- Behaviour
- Beverage
- Etc.
- The second indentation shows the direct subclasses of one
of the direct subclasses of object.
- Account does not have any subclasses. Note that
if you have created any subclasses for class Account,
they will only appear in the LB you used to create them.
- Amphibian, has direct subclasses of Frog and
Toad. (See note above).
- Behaviour, has a single direct subclass of ClassDescription.
- Etc.
- The third indentation, is similar to the second.
- Frog has a direct subclass of HoverFrog.
- Note that HoverFrog is NOT a subclass
of Toad
Now find your printout of the Collection class hierarchy. Then
in the Class browser.
- Using any of the 3 techniques (Exercises 2a or b) locate
the Collection class.
- Look at the 16 subclasses indented below the Collection
class.
- Compare this to printed diagram that has 19 subclasses
of Collection class.
- This is due to the fact that the printout was produced from
the larger list in LB-39, where 3 more classes were added.
If you have not spotted them they are listed in the table
above, under LB-39.
- Get a feel and background understanding of this very important
class hierarchy, by reading the various comments. At this
stage you are not going into any detail. When you reach the
various chapters in the M206 course you can repeat these exercises
in more detail.
- Find and verify the abstract classes.
Other classes that the course covers which you could look at are:-
- Account
- Boolean
- Frog, HoverFrog, and Toad. Depending where
you are in the course, use a Class brower before LB-21 if
required.
- Dialog- Look at the Class methods.
- Magnitude and its subclasses, especially
- Association
- Character
- Date Check out the Instance and class variables
and methods.
- Time
- Plane. The only class method, is very interesting,
pay particular attention to how it creates Student. The
only class method, is very interesting, pay particular
attention to how it creates a plane and sets the flight
identifier to aString.
- Student. The only class method, is very interesting,
pay particular attention to how it creates and initializes
an instance of Student.
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