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08/28/0615:04:^
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CS 61B Lab 1September 5-6, 2006 Goal:^ This^ lab
will^ give you practice editing and running Java programs, using^ Emacs,^
and^ accessing online Java documentation. There^ are^ several
things you will need to have your TA check off so you can get credit^ for^ this
lab.^ You can have them checked off all at once when you are finished,^ but
donât^ wait until the last minute--another lab may start as soon as^ yours^ ends,
so^ ask^ to be checked off when there is still plenty of time. Checkoffs^ will
not^ be^ done outside of lab. PART^ I:^ Getting
started^ (1 point) ---------------------------------1.^ If^ you^ are
officially registered for a lab--not on the waiting list--you must^ attend^ that
lab.^ Otherwise, find a lab that has space.
2.^ Pick^ up^ an
account^ form from your Lab TA.
3.^ Login^ to^ a
computer^ using the temporary password on your account form. Answer^ the^ questions
the computer asks.
Use whatever the registrar uses for
your^ given^ name
and^ surname.
Your registered name is used for grading. If^ you^ mess^ up
and^ need^ to correct your answers, run "register" from the Unix prompt.4.^ Warning:^
do^ not,^ at^ this time or any point in the future, delete the .login,^ .cshrc,
and^ .emacs files in your directory.
If you would like to
customize^ your
account,^ do so by adding new commands to the end of these files, not^ replacing
the^ files.
5.^ The^ rest^ of
this^ lab^ is a TEAM assignment, with two-person teams.
Introduce
yourself^ to^ the
people^ to your left and right (there is one point associated with^ knowing^
the^ names^ of two other people in the class).
Choose a partner.
If^ youâre^ the
odd^ person out in the lab, go ahead and begin, but if someone new arrives,^ partner
up^ with them and help them catch up.
PART II: Compile-time errors
(1^ point) --------------------------------------After logging in, you and your
partner^ may^
find^ it^ easier
to^ work^ on^
one
computer for a while.
However,^ you
should^ each^
be^ separately
capable^ of
demonstrating your knowledge
of^ the^ lab^ to
the^ TA^ when
itâs^ time^ to
check^ off.
- Make a lab1 subdirectory:mkdir lab12. Change into your lab1 directory:cd lab13. Copy the three lab files
by^ typing: cp $master/lab/lab1/*
IMPORTANT:^ You must type the
space^ and^ the
period^ for^ this
to^ work!
(Note:^ master is a shell variable
that^ refers^
to^ the^ cs61b
home^ directory,
which is /home/ff/cs61b.
Typing^ $master
evaluates^ that
variable.^ If
the^ cp
command above doesnât work,
it^ probably
means^ that^ something
is^ messed^ up
in
your login scripts, so talk
to^ your^ TA^
or^ lab^ assistant.)
- Load the program file Names.java
into^ Emacs^ using
C-x^ C-f.^ "C-x"
is^ read
"control x," and is typed by
holding^ down
the^ control
(Ctrl)^ key^ while
typing
"x".^ You may need to type the
full^ pathname
lab1/Names.java,
then^ hit^ Enter.
Names.java is a simple program
for^ performing
various^ string
operations^ on
a
name.^ It almost works, but
you^ need^ to
make^ some^ changes
so^ that^ it^
compiles
and runs correctly.5. Compile the program within
Emacs^ using: C-x C-eThis will build a command line
to^ run^ the^ Java
compiler:
javac -g"javac" is the name of the Java
compiler.^
"-g"^ is^ a^ switch
to^ tell^ the
compiler to generate the information
the^ debugger
will^ need.^
You^ need^ to
finish the command line by supplying
the^ name^ of
the^ file^ to^
be^ compiled:
javac -g Names.javaYou may instead type this command
in^ an^ xterm,
assuming^ youâre
in^ (your^ copy
of) the lab1 directory.6. You will find that javac
cannot^ compile
the^ program.
The^ code^ contains
two
syntax errors which you are
quite^ likely
to^ make^ when
you^ will^ write
programs. Use the control sequenceC-x âto jump directly to errors found
by^ javac.^
(Be^ sure^ to^ use
the^ single^ opening
quote, not the apostrophe.)
Figure^ out
whatâs^ wrong,
correct^ the^
errors,^ save
the file using "C-x C-s", and
compile^ the^
code.
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readme
PART^ III:^ Run-time
error (1 point) ----------------------------------1.^ Once^ javac
is^ able^ to compile the code, it will create a file called Names.class^ in
the^ same^ directory.
You can run this program using the Java interpreter.^
In^ a^ shell (an xterm or an Emacs buffer called shell), typejava Names Java^ automatically
appends the ".class" file extension on Names.class.
If you
accidentally^
type^ "java^ Names.class", Java will look for a file called "Names.class.class".The^ program^ has
an^ error.^ How can you tell there is something wrong?
This
type^ of^ error,
which^ occurs at run-time, tends to be significantly more difficult^ to^
correct^ than compile-time errors.
(Itâs still somewhat easier
than^ discovering
an^ error in which the program appears to finish without problems,^ but
is^ doing^ some computation incorrectly.)
The error message may be
hard^ to^ read^
at^ first,^ but it will allow you to answer certain questions:
What
is^ the^ method
(i.e.,^ procedure) that generated an error?
What is the line
number^ within
the^ file^ Names.java? The^ error^ is^
in^ one^ of^ the methods in the String class, which is a standard Java^ library.
Your^ textbooks contain some documentation of the Java library, but^ the^ best^
source^ is^ the online documentation.
To find this, start Firefox
by^ typingfirefox
Double-click^
on^ the^ URL^ window and type the URL for the class Web page.http://www.cs.berkeley.edu/Ëjrs/61b From^ there,^ you
can^ find a pointer to the "The Java 2 standard libraries API." There^ are^ two
libraries^ that you will be using early in the semester--the java.lang^ package
and^ the java.io package.
Documentation on String and other
standard^ data
types^ is^ found in java.lang, so go there and find the String class.^ There
is^ a^ lot^ of information, not all of which will make sense right now,^ but^ you^
should^ be^ able to find a description of the problematic String method.^ Be^ prepared
to^ show your TA or lab assistant how you found this information^ and
how^ you^ figured out from it what was wrong with the program. When^ you^ think
you^ have^ found the error, correct it, save the file, recompile it,^ and^ execute
it^ to^ see if the problem is solved. Aside:^ You^ may
think^ that the file produced by javac is named Names.class because^ the^ input
file^ is named Names.java.
Not so--the name of the .class
file^ is^ based
on^ the^ class name IN Names.java.
To experiment with this, change
the^ line^ "class
Names^ {" to "class NAMES {" and recompile using javac.
What
new^ file^ is^ created?
PART IV: Emacs help (1 point)-----------------------------1. Load the file "roster.txt"
in^ Emacs.^ You
will^ see^ an^
unsorted^ list
of
names, with each line in the
form^ <surname,
given^ names>.
You should use the help facilities
of^ Emacs^ (apropos
and^ info)^ to
find^ out^ how
to sort all these names by last
name.^ Then
sort^ the^ lines
of^ the^ file.
If^ you
are unfamiliar with the help
facilities^ type
"C-h^ ?",^ and
Emacs^ will^
guide^ you
through them.Save the result using "C-x C-s".If you have the course reader,
take^ a^ few^ minutes
to^ look^ through
it^ now^ so^ you
know exactly what information
you^ can^ look
up^ in^ it.^
Note^ that^ the
Emacs^ Quick
Reference Guide is in the very
front^ of^ the
reader.^ It^
will^ be^ handy
to^ keep
your reader by you whenever
youâre^ in^ the
lab.
PART V: Change your password
(no^ points) ----------------------------------------Change your accountâs password
using^ the^ "passwd"
command.^ Note
that^ it^ may
take a while for your password
change^ to^ be
stored^ in^ the
system^ files,
so^ you
may need to use your old password
if^ you^ login
in^ the^ interim.
Check-off---------When youâre done, show your
TA^ or^ lab^ assistant
your^ work,^
and^ explain^ how
you
accessed the Java String documentation
and^ found^ the
bug.
1 point:^ Show that your Names
program^ works. 1 point:^ Briefly explain how
you^ discovered
and^ fixed^ the
bugs,^ and^ show
how
you accessed the
Java^ String
documentation.
1 point:^ Show your sorted
roster.txt. 1 point:^ Tell the TA the names
of^ the^ students
next^ to^ you.
If you are inexperienced with
either^ Unix^
or^ Emacs,^ you
are^ strongly
encouraged
to attend one of the help sessions
on^ these^ topics
held^ by^ the^
Computer^ Science
Undergraduate Associaton (CSUA).
