CS288

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CS288

• Lab Exercise 1

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Open PersonGui Files

• Go to Course web site for PersonGui source files
• http//www.computing.surrey.ac.uk/courses/cs288/Ex
  amples/PersonGui
• Make copies of these files in you home folder and
  then open
• them in some editor (e.g. Emacs)
• PersonGui.java
• PersonMaker.java
• Person.java
• images.zip(unzip this file in the same directory
  as you have put the java files)
• Download a copy of these slides so that you can
  read them directly,and not simply view them in
  Internet Explorer. This is handy as you can then
  copy and paste code examples directlyfrom these
  slides.

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Read the slides on compiling Java Code
Make sure you have read the notes on compiling
Java Code http//www.computing.surrey.ac.uk/cour
ses/cs288/Labs/Compile_Java.ppt Compile
PersonGui.java. In a command window type javac
PersonGui.java now run the application java
PersonGui Right click the mouse in the large
text area. You should see a popup menu. Enter in
your name age height etc with this menu. Right
click the mouse and choose the create person
item. If you have installed the images correctly
from the zip file you should be able to choose a
suitable image at this point.
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How the PersonGui should appear
Choose this option should cause this dialog to
appear
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How the PersonGui should appear
Once you have picked an image it should then
appear as below.
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1 Search for Make_Person method
Find (could use Search in Emacs) the Make_Person
( ) method in PersonMaker.java
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1 Change the Make_Person method
Change the value of Make_Person to this
public String Make_Person ( )
Show_Attributes_InFrame () String
return_value "This Person
has these attributes \n " "\n\tFirst Name
\t " getFirstName() "\n\tLast Name \t
" getLastName() "\n\tHeight \t "
getPersonHeight() "\n\tAge \t "
getPersonAge() "\n" return return_value

Delete any .class files you have.Recompile and
rerun the code. This should not make any
difference to the way the code works. Test your
code to make sure that is true.
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1 Change the Make_Person method again
Change the value of Make_Person to this
public String Make_Person ( )
Show_Attributes_InFrame () String
return_value "This Person
has these FANTASTIC attributes \n "
"\n\tFirst Wonderful Name \t " getFirstName()
"\n\tLast Stunning Name \t "
getLastName() "\n\tLook at that Height \t
" getPersonHeight() "\n\tLook at that
Age \t " getPersonAge() "\n" return
return_value
Recompile and rerun the code. How does this
change the way the code works?
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1 Change the Make_Person method again
Change the value of Make_Person to this
public String Make_Person ( )
Show_Attributes_InFrame () String
the_empty_string "" //This will be handy for
the next part String return_value "This
Person has these FANTASTIC attributes \n "
return_value return_value "\n\tFirst
Wonderful Name \t " getFirstName()
return_value return_value "\n\tLast
Stunning Name \t " getLastName()
return_value return_value "\n\tLook at
that Height \t " getPersonHeight()
return_value return_value "\n\tLook at
that Age \t " getPersonAge() "\n" return
return_value
Recompile and rerun the code. How does this
change the way the code works?
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1 Set Empty String as Age
If we set the first name to be empty with the
menu
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1 Empty String as Age
Then we get a somewhat redundant message on the
screen
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1 Look in PersonGui.java
Change the Make_Person method so that if the user
enters a value for Age that is the empty string,
then the Make_Person returns a String that
says You entered an empty string for the first
name Instead of The Persons First Name is
"" If the user enters a non-empty string the
return value is unchanged. To do this you need
to use an if statement. See the Java Tutorial on
the course web site to see how if statements
work http//www.computing.surrey.ac.uk/courses/cs
288/Java_Documentation/Tutorial Go to the
section on Learning the Java Language then to
Language Basics then to Expressions, Statements,
and Blocks Also you need to understand how some
of the methods work for the String class. Go to
the Java SDK 2, Class Specifications link on the
course web site http//www.computing.surrey.ac.uk
/courses/cs288/Java_Documentation/docs/api/index.h
tml
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Search for the String class in this
column. Click on the String link
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Then click on the METHOD link at the top of
the page. Now find the equals method for this
class. This is useful if you want to know if a
string is the empty string.
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1 Change the Make_Person method again
Now change the Make_Person method again so that
if the User enters an empty string for the last
name of someone a more sensible string is
returned. Now change the method so that if a
users age is greater than 150.0 then the
return_string makes a suitable comment about how
incredibly old that person is.
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2 Find PersonMaker Constructor
Find the PersonMaker constructor in the
PersonMaker.java file
Find the reset_Person ( ) method.
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2 PersonMaker
Note the contents of reset_Person ( ) and
PersonMaker ( ) are the same. Define a third
method, public void set_default_values ( )
which is just a copy of the current reset_Person
method with new name. Now change reset_Person (
) and PersonMaker ( ) so that they simply call
the set_default_values ( ) method and do not
change any variable directly themselves.
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3 Removing Redundant Labels
Find the Person constructor method in the
Person.java file
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3 Removing Redundant Labels
Person ( ) creates a seperate JLabel for height,
age, first and last names. This is redundant.
Change the code so that Person ( ) only uses one
JLabel for all the strings that are to be
displayed. The purpose of this exercise is for
you to learn how to track all the data that is
associated with one variable, and also modify
that data for a different purpose.
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3 Removing Redundant Labels

• For example in this case, you will have to work
  out where
• variables
• first_text
• last_text
• age_text
• height_text
• are referred to in the rest of the method.
• You will have to figure out how to combine these
  variables into a single string (new String
  variable declaration).
• You will have to comment out those parts of the
  code that set up and use unwanted JLabels (such
  as label_first).
• You will have to create a new JLabel for the
  combined text.
• Now attach the JLabel somehow so that it replaces
  the four redundant labels.
• You will be able to do this simply by copying the
  way the other JLabels are defined, you dont need
  to understand what it all means yet.