Lecture 1

Lecture Topic:

Setting up the Java environment in UNIX.
• What's Java
  About Java
  Understanding Java
  Java Objects
  Java Basic

Setting up the Java Environment in UNIX.

 

1. You must be on a Sparc Station. CSE will not do. Permission will be denied if you try to run Java on CSE.
2. You may like to telnet to any sparc 5, for example, vampire;
3. set your path to the java directory in my home(place the following into your login-file):
   setenv PATH ${PATH}:/home/bunny/faculty/lyon/java/bin
   setenv JAVAHOME /home/bunny/faculty/lyon/java/bin
4. then type:
   rehash
   This will enable you to type:
5. which java
   and this should output the path of the java.
6. For example:
7. cat >>.login
8. ${PATH}:/home/bunny/faculty/lyon/java/bin
   setenv JAVAHOME /home/bunny/faculty/lyon/java/bin
   ^d
   source .login
   rehash
   which java

9. ---

   To compile:

UNIX:

    javac HelloWorldApp.java
 

DOS shell (Windows 95/NT):

    javac HelloWorldApp.java

Interpreting

UNIX:

java HelloWorldApp
 

DOS shell (Windows 95/NT):

java HelloWorldApp
 

Note: The argument to the Java interpreter is the name of the class, not the name of a file.

Into your .cshrc files, please place the following commands:

alias spps 'lpr -P$PRINTER -s' 
alias printer 'echo $PRINTER'
alias printer1 'setenv PRINTER hpps;echo hpps'
alias printer2 'setenv PRINTER lyon_gray; echo lyon_gray'
alias printer3 'setenv PRINTER dupascii; echo dupascii'
alias printer4 'setenv PRINTER dupps; echo dupps'
alias printers echo printers I know: hpps, lyon_gray, dupascii dupps

alias cancel 'lprm -P$PRINTER job '

alias q 'lpq -P$PRINTER'

Into your bin directory place and executible shell script into a file called sp:

#! /bin/csh -f
#
# by doug lyon 10/6/93
#
# Usage: sp <files>
 
if ($#argv == 0) then           # arguments?
        echo "Usage: $0 files"
        exit 1
endif
 
foreach file ($argv[*])         # expand argument word list
        echo spooling $file to $PRINTER
        xa2ps $file | lpr -P$PRINTER -s
end

Chmod to +x on sp, then rehash....

This should enable you to print ascii files to any printer... For printing postscript files, use the command: spps 'lpr -P$PRINTER -s '

To print sun snapshots from the sun

, use openwindows to save a screen shot as sun raster or any format file. Then use:

anytopnm - to convert a Sun raster file into a portable pixmap format...then use:

pnmtops - to convert a portable pixmap into color Encapsulated file to PostScript....then use:

spps (see above) to print the postscript to the printer of your choice.

For example, you may set a pipe alias in your .cshrc file so that a single command will print snap-shot...like this:

put the following into sp_shot:

#

# by doug lyon 4/8/97

#

# Usage: sp <files>

if ($#argv == 0) then # arguments?

echo "Usage: $0 raster_files_in_any_format"

exit 1

endif

foreach file ($argv[*]) # expand argument word list

echo spooling $file to $PRINTER

anytopnm $file | pnmtops >$file.ps

lpr -P$PRINTER -s $file.ps

echo " please remember to delete $file.ps later"

end

chmod +x sp_shot
rehash

A sample sp_shot is located in

/home/bunny/lyon/bin/sp_shot

What is Java?

· An Object-Oriented language, with syntax which is like C/C++.
• It's a language which has security features
• Multi-platform
  • Sun
  • Mac
  • Win95/NT
  • Linux
  • Next
  • Irix
  • Amiga

  · Java is Strongly type.
  

About Java

· C syntax with C++ like classes.
· Strong Type --IEEE floating point(32 bit only)
• Java does not have:
  • pointers
  • pointer case
  • free
  • enum
  • struct
  • union
  • a preprocessor

Understanding Java

Java is a "simple, object-oriented, distributed, interpreted, robust, secure, architecture neutral, portable, high-performance, multi-threaded, and dynamic language."

Java is compiled and interpreted
A Java program is compiled into a class file.


• Class files are not executable because they do not contain instructions directly understandable by the processor. Java programs are compiled to a byte-code format. This byte code represents machine language instructions for a virtual microprocessor, which doesn't exist as an actual chip inside your computer. This virtual microprocessor is called the Java Virtual Machine. The Java interpreter implements the Java Virtual Machine in software so that it can execute Java class binary files.(Ed Anuff, p16)

Java Objects

Object = Instance of a Class (classname).
Ex.
Rectangle r = new Rectangle(); // rectangle is a class
Integer p = new Integer(); // Integer is a class


Member data = Instance Variables = Properties

Methods = Member functions
Call a method = Send a message = Invoking a method

Java Basic

Scalar Type
Boolean(TRUE, FALSE)
Numeric{Integer, Real}

Integer Type:
char - 16 bits unicode character
byte - 8 bits signed -128..127
short - 16 bits signed -32768..32767
int - 32 bits signed - 2e(32-1) .. 2e(32-1)-1
long - 64 bits signed - 2e(64-1)...2e(64-1)-1

Real Type:
float - 32 bits float point IEEE 754-1985 6-7 significant
double - 64 bits float point IEEE 754-1985 6-7 significant

Sample Quiz

1. Applets are:
     a. little apples
     b. little applications
     c. often run from a web page
     d. stand-alone applications