Extra Credit Practice Exercise # 1

CS 115

EXTRA CREDIT PRACTICE EXERCISE # 1

The purpose of this exercise is to:

1. Familiarize you with using the text Editor Notepad++ to write a very

basic Java program.

2. How to upload an assignment on Blackboard.

 FOLLOW STEP BY STEP THE INSTRUCTIONS BELOW AND IMPLEMENT THE

SAMPLE PROGRAM DISCUSSED.

 MUST DEMOSTRATE IT TO THE TA BEFORE SUBMISSION ON BLACKBOARD.

 MUST BE SUBMITTED AND TIMESTAMPED BY BLACKBOARD NO LATER THAN

THE TIME THE CLASS IS OVER.

 DO NOT HESITATE TO HELP THE STUDENT NEXT TO YOU IF YOU KNOW THE

ANSWER. YOU ARE ALLOWED TO DO THATDURING THE EXTRA CREDIT

EXERCISES.

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To create a java program we will need:

1. A text editor program (application). The one we are going to use is called

Notepad++ . The text editor is where we write the program using java keywords

and symbols. 1 2. The java compiler (available on the computer station).

3. The java interpreter (available on the computer station)

TASK: WRITE A BASIC JAVA PROGRM THAT DISPLAYS THE MESSGE “This is a Java program”.

STEP 1: Open the text editor program called Notepad++ by clicking on the icon representing the program on your Desktop. From the menu toolbar of Notepad++ choose

FILE->New

STEP 2:

Let us type the program (java instructions) shown below in italics:

Note: In typing the program I would like you to follow the indents as shown. Advance the

tabs to maintain the position of the curly brackets and the typing of the programming

instructions as shown.

In addition to the programming instructions, we will add some comments.

Comments are notes that we make that are not part of the programming instructions.

These notes could be the: date the program was written, the name of the person who

wrote it, or explanatory notes about the program. The compiler disregards those

comments if they are preceded with the two slashes. Make sure that you type the

comments as shown preceded by //)

BEFORE YOU TYPE THE PROGRAM CREATE ON THE DESKTOP A NEW FOLDER AND

NAME IT extracredit1. NOTE: THIS DOCUMENT SHOULD ALSO BE SAVED IN THE

2 SAME FOLDER BY DOWNLOADING IT FROM THE WEB SITE :

http://www.cs.iit.edu/~cs115/schedule.html

ON THE NOTEPAD++ SCREEN TYPE THE FOLLOWING PROGRAM EXACTLY AS SHOWN

BELOW (DO NOT CUT AND PASTE!!):

public class MyFirstProgram

//double slashes are used for comments

//anything after the double slashes is disregarded by the compiler

//the name of the class is: MyFirstProgram

public static void main (String[] args)

System.out.println(“This is a Java program”);

MAKE SURE THAT YOU USED THE CURLY BRACKETS AFTER THE NAME OF THE CLASS

AND AT THE END OF THE PROGRAM. SOLID PARENTHESIS AFTER main.

MAKE SURE ALSO THAT INSIDE THE PARENTHESIS (AFTER main) THE BRACKETS

AFTER THE KEYWORD String ARE SOLID BRACKETS.

Definitions:

The name after the keyword class (MyFirstProgram in this example) is called the

class name.

3 The file that you create by typing the above code is called the source code file.

The file has to be saved with the name: the class name that you provided followed by the extension .java

In this example the source code file will be saved as: MyFirstProgram.java

STEP 3: Now, we are ready to save the program in a file WHICH NEEDS TO BE IN THE

FOLDER extracredit1. Choose from the Notepad++ menu File->SaveAs

MAKE SURE THAT THE PROPER DIRECTORY (FOLDER) IS SHOWN WHERE YOU WANT TO

SAVE THE SOURCE CODE FILE. YOU WANT TO SAVE THE SOURCE CODE FILE YOU TYPED IN

THE FOLDER extracredit1.

NAME THE FILE (REFERRED TO AS THE SOURCE CODE FILE) THAT YOU CREATED USING THE

SAME NAME AS THE NAME OF THE CLASS , AND THEN ADD THE FILE EXTENSION .java AFTER

THE NAME. i.e. MyFirstPorgram.java for our program that we are working on.

It should be typed using the same capitalization as the name of the class in the source code file. In the example picture below the program is saved directly on the Desktop (that is not what you want, you want to save it in the folder you created:extracredit1).

CLICK save.

4 STEP 4: IN WINDOWS EXPLORER (OR THE DESKTOP) GO TO THE FOLDER extracredit1 AND

VERIFY THAT THE FILE MyFirstProgram.java IS THERE INSIDE THE FOLDER.

Definitions:

The next step will create the code that the computer can understand with the help of the java compiler. The file created when the compiler tool compiles the source code file is called the

“compiled file” or “the .class file” or “the bytecodes file”.

The compiler is a software tool that we will use to compile the source code file in order to create the bytecodes (compiled) file. The compiler will save the bytecodes file in the same folder as the source code file using the same name as the source code file except that it changes the

5 extension from .java to .class (i.e. MyFirstProgram.class will be the new file created by the compiler).

The compile will not produce the bytecodes file (MtFirstProgram.class in our example) unless everything is correct. If there is a mistake (a misspelling or the wrong symbol etc), the compiler will produce error messages at the bottom of the Notepad++ screen. An error message will identify the line by number where the compiler found an error as well as some message about the error.

STEP 5: WE ARE GOING TO USE THE JAVA COMPILER TO COMPILE THE SOURCE CODE FILE WE

CREATED. THERE ARE A COUPLE OF DIFFERENT WAYS WE CAN DO IT.

1. WE COULD DO IT DIRECTLY FROM Notepad++ TOOL BAR (AT THE TOP OF THE SCREEN) BY

GOING TO “MACRO” MENU AND CHOOSING THE “COMPILER JAVA” MENU ITEM. .

2. WE COULD DO IT BY OPENING A DOS WINDOW AND TYPING THE PROPER COMMAND. THIS

IS CALLED COMMAND LINE. THE OUTPUT WILL APPEAR ON THE DOS WINDOW (SOMETIMES

REFERRED TO AS THE DOS PANE).

WE WILL COMPILE BY USING METHOD 1 FIRST:

With your source code file open in Notepad++ go to the tool bar and choose macro->compile java. As you have noticed the Notepad++ screen is split into two parts. The bottom part displays the result of the compilation process. If everything was typed correctly the bottom part will display the message shown in the picture below.

6 7 IN THIS PICTURE THE COMPILER INDICATES THAT EVRYTHING WAS O.K. WITH OUR PROGRAM

(Process finished exit(0)).

STEP 6: IN THE NEXT PICTURE A MISTAKE WAS ON PUPRPSE MADE IN ORDER TO DEMONSTRAT

EWHAT THE COMPILE WILL SHOW AT TH EBOTTOM OF THE SCREEN (THE KEYWORD Claas was misspelled as clas).

SIMULATE A MISTAKE IN THE PROGRAM AND RECOMPILE. OBSERVE THE MESSAGE AT THE

BTTOM OF THE SCREEN.

STEP 7: SECOND METHOD OF COMPILING BY USING COMMAND LINE DOS COMMANDS

FROM Start Menu-> All Programs CHOOSE Assessories->Command Prompt

A BLACK SCREEN WINDOW WILL APPEAR ON THE SCREEN WHICH CALLED DOS WINDOW. THE

PICTURE BELOW IS A DOS WINDOW.

9 NOTICE THAT THE SCREEN SHOWS A PATH ON YOUR COMPUTER LIKE:

C:\Users/George> _

OR IT MAY BE A DIFFERENT PATH DEPENDING ON YOUR USER ACCOUNT. WE NEED TO

NAVIGATE TO WHERE THE FOLDER WITH OUR FILE MyFirstProgram.java IS LOCATED. WE CAN

MOVE UP OR DOWN THE DIRECTORY PATH BY USING DOS COMMANDS. i.e. C\User/George> cd..

 TYPING cd FOLLOWED BY TWO DOTS AND PRESSING Enter KEY, MOVES THE CURSOR TO

THE LOWER DIRECTORY.

C\User>

10  TYPING THE SAME AGAIN AND PRESSING THE Enter KEY, MOVES THE CURSOR DOWN

ONE MORE DIRECTORY

C\User>cd..

NOW THE CURSOR IS AT C:\>_ a) THE COMMAND cd FOLLOWED BY SPACE AND THEN THE NAME OF THE DIRECTORY

(FOLDER) THAT WE WANT MOVES THE CURSOR TO THAT DIRECTORY.

C:\>cd PRACTICEEX1

PRESS Enter KEY.

RESULTS IN

C:\PRACTICEEXE1>_ b) TYPE THE PATH TO YOUR DESKTOP FROM USER PATH AND THEN TO YOUR

FOLDER extracredit1 . ASK THE TA FOR HELP IF YOU DON’T UNDERSTAND THE

ISNTRUCTIONS. c) THE COMMAND dir WILL DISPLAY THE FOLDERS AND FILES IN A SPECIFIC PATH

I.E C:/users/myloginname/Desktop/extracredit1>dir

SHOWS ON THE DOS WINDOWS ALL THE FILES IN FOLDER extracredit1 (note that

the [path could be different in your computer). YOU SHOULD TRY TO VERIFY

ONCE AGAIN THAT THE FILE MyFirstProgram.java IS THERE BY TYPING THE DOS

COMMAND dir.

NOW WE ARE READY TO USE THE DOS COMMAND THAT WILL ALLOW US TO

COMPILE OUR SOURCE CODE.

11 (YOU SHOULD DELETE THE COMPILED FILE FROM THE PREVIUOS STEP 5 ATTEMPT

BEFORE YOU RE COMPILE IN THIS STEP).

TYPE THE COMMAND AS FOLLOWS:

C:/somepath/Extracredit1>javac MyFirstProgram.java

NOTICE THAT THERE IS SPACE AFTER javac (which is the command for the java

compiler)

PRESS Enter KEY.

THE FILE MyFirstProgram.class IS CREATED . THIS FILE IS CALLED THE BYTECODES FILE. d) TYPING THE DOS COMMAND dir WILL DISPLAY ALL FILES AGAIN. YOU SHOULD BE ABLE

TO VERIFY THAT THIS NEW FILE WAS CREATED. e) HERE IS AN EXAMPLE SCREEN THAT SHOWS HOW I GOTTO THE DESKTOP ON MY

LAPTOP (the path may be a little different in your computer):

C:\Users\George>cd Desktop

C:\Users\George\Desktop>cd Practice1

C:\Users\George\Desktop\Practice1>

Typing the DOS command dir after the above prompt will display all the file residing in

folder Practice1 (that is the file we created and saved there under the name

MyFirstProgram.java)

12 STEP 7:

Definitions:

A java program is executed ( OR OTHER TERMS FOR THE SAME THING ARE : RUN OR

INTERPRETED) by using the java interpreter software tool. The java interpreter translates the bydecode symbols in the bytecodes file into machine instructions that the computer understands.

We can interpret the program we wrote from the Notepad++ toolbar by clicking on

MACRO-> java run MENU ITEM. THE OUTPUT WILL APPEAR ON THE BOOT PART OF

THE NOTEPAD++ SCREEN.

Observe the output by following the is method of running the program.

STEP 8: Let us now interpret (execute) the program we created by using the DOS window as an alternative way. In the same DOS window as before type the command to call the java interpreter:

….extracredit1>java MyFirstProgram

NOTICE THAT THE COMMAND IS java (not javac) THEN SPACE AND THEN THE NAME OF THE

BYTECODES FILE WITHOUT THE EXTENSION .class.

THE OUTPUT OF THE PROGRAM SHOULD APPEAR ON THE DOS WINDOW.

THE PICTURE BELOW ILLUSTRATES THE PROCESS DESCRIBED. THE DIRECTORY PATHS IN YOUR

CASE MAYBE DIFFERENT THAN THE PICTURE.

13 COMPILER GENERATED ERROR OUTPUT OF PROGRAM BECAUSE THE .java EXTENSION WAS NOT TYPED AFTER THE NAME OF THE SOURCE

CODE FILE

STEP 7: NEXT I WOULD LIKE YOU TO UPLOAD THIS EXTRA CREDIT PRACTICE EXERCISE ON

BLACKBOARD. BEFORE YOU DO THIS STEP YOU MUST SHOW TO YOUR TA OR THE 14 INSTRUCTOR THAT YOU COMPLETED THE WORK CORRECTLY. THE TA OR THE

INSTRUCTOR MUST APPROVE IT FIRST BEFORE YOU CAN UPLOAD YOUR WORK ON

BLACKBOARD.

a) Zip the two files MyFirstProgram.java and MyFirstProgram.class as well as

this WORD document with the answers to the above questions, into a zipped

file named yourfirstname_yourlastnam_PracticeEx1.zip

Ask myself or your TA assigned to you for help IF YOU DON’T KNOW HO WTO

ZIP GROUP OF FILES.

b) Open your Blackboard account for this class and upload the zipped file on

Blackboard under the assignment folder Extra Credit # 1 on Blackboard.

PLEASE MAKE SURE THAT YOU UPLOADED THE FILE ON THE CORRECT FOLDER> TAKE

YOUR TIME/ASK FOR HELP.

NOTE: YOU NEED TO CLICK ON SUBMIT BUTTON IN YOUR BLACKBOARD SCREEN.

STOP BY THE TA TO VERIFY CORRECT SUBMISSION OF THE FILE.

THIS PROCESS WILL BE REPAETED A NUMBER OF TIMES THROUGHOUT THE SEMESTER

IN DOING SUBMISSIONS. IT HAS TO BE DONE CORRECTLY OTHERWISE WE CAN”T

RETRIEVE YOUR FILES FOR GRADING!

STEP 8: FINALLY, I WOULD LIKE YOU TO REPEAT THE ABOVE PROCESS (STEPS 1-6 BUT

NOT THE SUBMISSION STEP) AT YOUR OWN TIME AFTER THE CLASS IS OVER, IN YOUR

OWN LAPTOP (OR DESKTOP) PROVIDED THAT YOU HAVE INSTALLED THE JDK IN YORU

LAPTOP (see Lecture2_2 for installation instructions OR SEE ME IF YOU NEED HELP

INSTLLING IT). 15 QUESTIONS SECTION: AFTER COMPLITIG THE ABOVE 8 STEPS SHOW YOUR WORK TO

THE TA AND RECEIVE APPROVAL TO PROCEED WITH THE REST OF THE EXERCISE:

NOW, ANSWER THE FOLLOWING QUESTIONS BY TYPING THE ANSWERS ON THIS DOCUMENT.

(NOTE: IT IS ASSUMED THAT YOU HAVE DOWNLOADED AND SAVED THE DOCUMENT IN YOUR

FOLDER: extracredit1)

1. A Java program (source code file) is saved in a file named:

a) java.myprogram always.

b) The same name that you gave to the class in the source code, followed by the

extension .java

c) Any name that you want to save the source code file followed by the extension

d) Just the name of the class that you typed in the source code without any

extension.

Answer: ______

2. In order to execute a java program

a) The java interpeter tool has to be used on the bytecodes file

b) The compiler tool has to be used on the bytecodes file.

c) The compiler interprets the source code file and executes it.

d) The interpreter is used on the file that has the .java extension.

Answer: ______

3. Answer the following exercises from your text Chapter 1 (pages 35 – 37)

16 exercises 1:______

exercise 2:______

exercise 3:______

exercise 9:______

exercise 11:______

exercise 13:______

exercise 14:______

THE SUBMISSION IS VALID IF IT IS DONE BY TEHE ND OF THE CLASS PERIOD!!

SUBMISSION INSTRCUTIONS: AFTER THE TA CHECKS THE ACCUARCY OF YORU ANSWERS TO THE

ABOVE QUESTIONS DO THE FOLLOWING:

1. CHECK O MAK ESURE THATHE FOLLOWING FILES ARE INSIDE YORU FOLDER extracredit1:

MyFirstProgram.java

MyFirstProgram.class

Practice1.doc (this document with the answers to the questions).

2. ZIP (COMPRESS) THE FOLDER extracredit1. RIGHT CLICK ANDCHOOSE COMRESS USING .zip

CHOICE. THE RESULT WILL BE A NEW FILE NAMED extracredit.zip ON YOUR DESKTOP.

3. OPEN BLACKBOARD AND GO TO YOUR STUDENT ACCOUNT. SUBMIT THE FILE

extracredit1.zip ON YOUR BLACKBOARD ASSIGNMENTS SCREEN BY CHOOSING THE

ASSIGNMENT “EXTRA CREDIT # 1”. ASK FOR HELP IF YOU NEED IT.

17 Copyright: Fall 2015 George Koutsogiannakis, IIT.