ITI 1221, Introduction to Computing - II Lab-1

1. ITI 1221, Introduction to Computing - IILab-1 Dewan Tanvir Ahmed University of Ottawa

2. Contact Information • Email: dahmed@site.uottawa.ca • Office hour: Mon 1400~1600 • Office location: • Discover Lab • Room 5040 • SITE • Website: http://www.site.uottawa.ca/~dahmed

3. General Instructions for Assignments • Assignment URL: • http://www.site.uottawa.ca/~turcotte/teaching/iti-1221/assignments/ • Notes • Do the assignments individually or a team of two • Submission by WebCT • Don’t forget to hit Submit button • Indent your code properly • Late assignments will not be accepted; they will receive a grade of 0; • It is not acceptable to hand in code that does not compile • Maximal mark in this case be 30% • A Tour: • http://www.site.uottawa.ca/~turcotte/teaching/iti-1221/assignments/directives.html

4. General • Late assignments will not be accepted; they will receive a grade of 0; • Assignments must be done in teams of two or individually; • Assignments are due on Sundays by 23:00 (11 p.m.)

5. Identify yourself • README should be a text file and not a Word document • All this should appear in all of the following places: • at the beginning of each program/class (in comments) • at the beginning of each program's output Example of a class header: // Author: Linus Torvald // Student number: 111223 // Course: ITI 1221-A // Instructor: Marcel TURCOTTE // Tutorial: DCG-2 // Teaching Assistant: Dewan Tanvir Ahmed // Assignment: 4 // Question: 2

6. Restrictions and Marking scheme • Restrictions • Everything you hand in • must compile and run using the J2SE 1.4.2 system on SITE's PCs; • The maximum grade for an assignment that does not compile is 30%; • You may only use features and library methods of Java • that have been presented in class or tutorials at the time an assignment is due. • Marking Scheme • based on the code's correctness and quality • Each part of your solution (e.g. each method) • assessed individually • relative to the conditions and requirements stated in the questions

7. Handing an assignment • All assignments must submitted electronically using your virtual campus account. • follow the guidelines for naming the files (specific to each assignment); • virtual campus: • virtualcampus.uottawa.ca • For teams of two students • Only one of the two students submits a copy of the assignment • Clearly identify your partner and yourself. • Assignments that do not conform to the above procedure will not be marked; • Never upload the the byte-code files (files ending with the suffix .class); • All the assignments are systematically re-compiled.

8. Programming Standards • Follow the standard code conventions for Java • http://java.sun.com/docs/codeconv/html/CodeConvTOC.doc.html • Identifiers • class and interface names begin with an upper case letter; • method and variable names begin with a lower case letter • except for the constructors • Several words may construct a name • not separated by underscores • and the second and subsequent words should start with an upper case letter • Class: StackArray, • Variable: maxValueAtrribute

9. Programming Standards (cont..) • names of constants • Single word: PI • Multiple words: MAX_VALUE • a method name should begin with a verb • computeMaxmimum not just maximum • a method whose primary purpose is to access an instance variable • getAttribute • setAttribute • isAttributeEqualTo(value) • Emphasis relation

10. Variables • Only declare variables that are actually used • Do not allocate memory unless necessarily • Do not use the same variable for different purposes • Local variables should not be confused with instance variables: • declare each variable in its appropriate place; • Every variable should have a comment describing its purpose. • Be brief. • This is called a data dictionary • it should be placed • at the beginning of every method, • either before or beside the declarations.

11. Program Structure • Write code with good structure • Introduce your own abstract classes and/or interfaces and • decompose your algorithms/methods into meaningful sub-algorithms/methods • Each method, including "main“, should be preceded by comments • describing its purpose and • the algorithm it uses • if the algorithm is very simple, it needn't be described • should be BRIEF. • Your program must be indented in a systematic way that reflects the nesting of its statements.

12. Input/Output • Output should be • nicely spaced and • easy to understand. • Every value in your output • must print a short message explaining the meaning of the value • Before your program reads values from the keyboard • it must print a prompt describing what the user is required to enter

13. Lexical Scope • Definition: • The scope of an identifier is fixed at compile time to some region in the source code containing the identifier’s declaration. • This identifier is only accessible within that region. • Examples:

14. More Examples class Scope{ static int i; public static void main(String[ ] argv){ int i; i = 50; System.out.println("Value of i: " + i); } } class Scope{ static int i; public static void main(String[ ] argv){ System.out.println("Value of i: " + i); } } class Scope{ public static void main(String[ ] argv){ int i; i = 10; if(i<20){ int save = i*3; } System.out.println("Value of save: " + save); } } class Scope{ static void increment(){ i++; } public static void main(String[ ] argv){ int i; i = 10; increment(); System.out.println("Value of i: " + i); } }

15. Data Type Conversion • Primitive data types • int • long • double class DataType{ public static void main(String[] agrv){ System.out.println("An \"int\" can hold a maximum of " + Integer.MAX_VALUE); System.out.println("An \"long\" can hold a maximum of " + Long.MAX_VALUE); System.out.println("An \"double\" can hold a maximum of " + Double.MAX_VALUE); } } An "int" can hold a maximum of 2147483647 An "long" can hold a maximum of 9223372036854775807 An "double" can hold a maximum of 1.7976931348623157E308

16. Type Conversion • Implicit • The ability of some compilers to automatically insert type conversion functions where an expression of one type is used in a context where another type is expected. • Explicit • Type casting • Narrowing and the possibility of data loss

17. Type Conversion class DataType{ public static void main(String[] agrv){ int x, z; double y; x = 7; y = 8.3; System.out.println("Value of the expresion <x*y>: " + x*y); z = (int)(x*y); System.out.println("Value of z: " + z); z = (int) ((double) x * y); System.out.println("Value of z: " + z); z = x*(int)y; System.out.println("Value of z: " + z); y = x*y; System.out.println("Value of updated y: " + y); } } 58.1 58 58 56 58.1

18. Wrapper Classes • Useful to convert data read from the keyboard class WrapperClass{ public static void main(String[] argv) { int i; double d; i = Integer.parseInt("78"); d = Double.parseDouble("45.0215"); System.out.println("Integer has a value of " + i); System.out.println("Double has a value of " + d); } }

19. Modulo Arithmetic • Division ( / ) • Reminder/Modulus ( % ) • Example: • 11 / 4 (2) • 11 % 4 (3) • Brain storming • 14/3 + 17%5 ? • (your student number % 3) ? • Just make it interesting. • Reverse a positive number ? • Example: • Input: 1234 • Output: 4321 • Can you do it?

20. Modulo Arithmetic (Cont..) class Modulo{ int n; Modulo(int n){ this.n = n; } int reverseNumber(){ int rem, rev; rev = 0; while(n!=0){ rem = n % 10; n = n / 10; rev = rev*10 + rem; } return rev; } public static void main( String [] args){ Modulo m = new Modulo(1234); System.out.println("Reverse of number: " + m.n + " ....." + m.reverseNumber()); } }

21. Application Program Interface (API) • A tour: http://java.sun.com/j2se/1.4/docs/api/overview-summary.html • Information is presented in a nice hierarchy • Object • String • Number • Integer • Double • Example of overriding class Override{ public static void main(String[] argv) { Override or = new Override(); System.out.println("What is this? " + or.toString()); } } class Override{ int x; public String toString(){ return "Overrirded: " + x; } public static void main(String[] argv) { Override or = new Override(); or.x = 15; System.out.println("What is this? " + or.toString()); } }

22. Compile and Run • Write a program that will print our name and student Id. • Compile it • Run it • Group formation among students • Use DrJava

23. Command Line • It is a way to pass information to the program • Say, java Test marcel 123 true • public static void main (String [] args) • What is args? • Reference that designates an array of String • Each element of this array is also a reference • Write a program that will take 3 arguments from command prompt and print their summation • Write a class that has a main method that displays the arguments on command line

24. Programming Editor • Good programming Editor • Saves time • Takes care indentation • Color coding helps finding the syntax errors. • Let’s go and play with Editor

25. Assignment 0 • Objective • Editing, compiling and running a simple Java program • Raising awareness about the university policies for academic frauds • Submitting an assignment using virtual campus online submission system. • A tour: • http://www.site.uottawa.ca/~turcotte/teaching/iti-1221/assignments/ • Editing, compiling and running…Java program • Syllabus • Academic fraud • Online submission • Directives • Files • README • Ao.java

26. Assignment 0 (Cont..) • public static void displayStudentInfo( ) • Displays the student name, id and laboratory section • public static String[] findAndReplace( String[] in, String[] what, String[] with ) replacement[ 0 ] = new String( "You" ); replacement[ 1 ] = new String( "should" ); replacement[ 2 ] = new String( "your" ); query[ 0 ] = text[ 0 ]; query[ 1 ] = text[ 1 ]; query[ 2 ] = text[ 4 ]; text[ 0 ] = new String( "I" ); text[ 1 ] = new String( "have" ); text[ 2 ] = new String( "never" ); text[ 3 ] = new String( "let" ); text[ 4 ] = new String( "my" ); text[ 5 ] = new String( "schooling" ); text[ 6 ] = new String( "interfere" ); text[ 7 ] = new String( "with" ); text[ 8 ] = new String( "my" ); text[ 9 ] = new String( "education" ); String[ ] result; result = findAndReplace( text, query, replacement ); Youshould never let your schooling interfere with your education should your You

27. Happy Programming!!!

28. To whom Java is new! • The URL for ITI 1220 is • http://www.site.uottawa.ca/~awilliam/iti1220 • If you need help on setting up Java on home computers page: • http://www.site.uottawa.ca/~awilliam/iti1220/WorkAtHome.html • It is important to set the PATH as described at the following page • http://java.sun.com/j2se/1.5.0/install-windows.html • Course website: • http://www.site.uottawa.ca/~turcotte/teaching/iti-1221/ • Hands on practice