Comp 114 Foundations of Programming Instructor: Prasun Dewan

Topics Assumed & Reviewed Types –int, double, char, String Variables, constants, expressions Arrays Assignment, conditionals, loops Procedures/Functions/Subroutines/Methods Parameters/arguments

Hello World

package warmup; public class AHelloWorldGreeter { public static void main (String[] args) { System.out.println ("Hello World"); } Array of user-supplied arguments main header directory/library Keyword Predefined Programmer- defined

Main Arguments user-supplied argument

Main Arguments package warmup; public class AnArgPrinter { public static void main (String[] args) { System.out.println (args[0]); } First argument args[0] args[1] Second argument...

Main Arguments user- supples no argument package warmup; public class AnArgPrinter { public static void main (String[] args) { System.out.println (args[0]); } program refers to argument array element exception!

Safe Arg Printer

Safe Arg Printer (edit in class) package warmup; public class ASafeArgPrinter { public static void main (String[] args) { //args.length gives number of elements in args array. }

Safe Arg Printer package warmup; public class ASafeArgPrinter { public static void main (String[] args) { if (args.length == 1) System.out.println (args[0]); else { System.out.println("Illegal no of arguments:" + args.length + ". Terminating program"); System.exit(-1); }

if-else Statement if ( ) else

if-else Statement true false

Compound Statement if (args.length == 1) System.out.println (args[0]); else { System.out.println("Illegal no of arguments:" + args.length + ". Terminating program"); System.exit(-1); }

Nested if-else public static char toLetterGrade (int score) { if (score >= A_CUTOFF) return 'A'; else if (score >= B_CUTOFF) return 'B'; else if (score >= C_CUTOFF) return 'C'; else if (score >= D_CUTOFF) return 'D'; else return 'F'; }

Nested if-else if (score >= A_CUTOFF) return 'A'; else if (score >= B_CUTOFF) return 'B'; else if (score >= C_CUTOFF) return 'C'; else if (score >= D_CUTOFF) return 'D'; else return 'F';

Nested if-else

If Statement if (args.length = = 1) System.out.println (”args[0]”); if ( ) ;

Printing Multiple Arguments

Printing Multiple Arguments (edit in class) package warmup; public class AnArgsPrinter { public static void main(String[] args){ }

Printing Multiple Arguments package warmup; public class AnArgsPrinter { public static void main(String[] args){ int argNo = 0; while (argNo < args.length) { System.out.println(args[argNo]); argNo++; }

if vs. while Statement if ( ) ; while ( ) ;

if Statement true false

while Statement true false

while loop true false

Scanning Problem

char Constants char {letters, digits, operators...} ‘a’ ‘A‘ ‘1’ ‘< ‘ ‘’ 16 bits ‘ ‘’’ ‘\’’ Escape sequence ‘\n’ newline ‘ ‘\’ ‘\\’

Useful Escape Sequences

Ordering Characters ‘’‘a’…. position in ordered character list ordinal number (integer code) ….

Ordering Characters ‘’‘a’…. ‘b’‘c’‘z’…. ‘’‘A’…. ‘B’‘C’‘Z’…. ‘’‘0’…. ‘1’‘2’‘3’…. ‘a’ > ‘b’  false ‘B’ > ‘A’  true ‘4’ > ‘0’  true ‘0’ > ‘’  true ‘a’ > ‘A’  ??? ‘a’ > ‘0’  ???

Converting between Characters and their Ordinal Numbers (int) ‘a’  ordinal number of ’a’ (char) 55  character whose ordinal number is 55 (int) ‘’  0 0 (char) 0  ‘’ (int) ‘d’  ??? (char) 1  ??? (char) -1 (int) ‘c’ - (int) ‘a’  2 2 ‘c’ - ‘a’  2 2 Implicit cast to wider type (char) (‘c’ - 2)  ‘a’ (char) (‘A’ + 2)  ‘C’ (char) (‘C’ - ‘A’ + ‘a’)  ‘c’

String constants String{sequences of characters} “hello” “123” “hello 123” “a” variable size ‘a’ “” “hello\n\n123” “\”“\\” Object Type

Accessing String Components String s = “hello world”; s[0] s[1]... s.charAt(0)  ‘h’ s.charAt(1)  ‘e’ s.charAt(-1) s.charAt(11) StringIndexBounds exceptiom index s.length()  11 “ ”.length()  1 1  0 0

Accessing SubString “hello world”.substring(4,7)  s.charAt(beginIndex).. s.charAt(endIndex-1) s.substring(beginIndex, endIndex)  “o w” “hello world”.substring(4,4)  “” “hello world”.substring(7,4) StringIndexBounds exceptiom

String Processing int i = 0; while (i < s.length()) { System.out.println (s.charAt(i)); i++; } prints each character on separate line

Dissecting a Loop int i = 0; while (i < s.length()) { System.out.println (s.charAt(i)); i++; } loop condition loop body

Finer-grained Dissection int i = 0; while (i < s.length()) { System.out.println (s.charAt(i)); i++; } loop condition real body Resetting loop variable initalizing loop variables for (int i=0; i<s.length(); i++) System.out.println(s.charAt(i));

Meaning of For Loop S1; while ( E) { S3; S2; } for (S1; E; S2) S3 for (; E; S2) S3 while ( E) { S3; S2; } for (; E; ) S3 while ( E) { S3; } for (; ; ) S3 while ( true) S3;

Scanning Problem

Scanning Scanning image for text. Scanning frequencies for radio stations. Finding words in a sentence Finding identifiers, operators, in a program

Scanning JohnF.Kenndye token Input stream Token Stream token

Algorithm JohnF.Kenndye marker 0 Output: J

Algorithm JohnF.Kenndye marker 1 Output: J String inputLine

Algorithm JohnF.Kenndye marker 2 Output: J

Algorithm JohnF.Kenndye marker 5 Output: JF

Algorithm JohnF.Kenndye marker 6 Output: JF

Algorithm JohnF.Kenndye marker 8 Output: JFK

Algorithm JohnF.Kenndye marker 9 Output: JFK

Algorithm JohnF.Kenndye marker 14 Output: JFK

Solution (edit in class) package warmup; public class AnUpperCasePrinter { public static void main(String[] args){ }

Solution package warmup; public class AnUpperCasePrinter { public static void main(String[] args){ if (args.length != 1) { System.out.println("Illegal number of arguments:" + args.length + ". Terminating program."); System.exit(-1); } System.out.println("Upper Case Letters:"); int index = 0; while (index < args[0].length()) { if (isUpperCase(args[0].charAt(index))) System.out.print(args[0].charAt(index)); index++; } System.out.println(); } public static boolean isUpperCase(char c) { return (c >= 'A') && (c <= 'Z'); } Function call Actual parameter Function definition Formal parameter

Creating JBuilder Project

Adding a Class

Editing the Class

Saving the Class

Running the Class

Viewing the Results

Running with arguments

Setting a break point

Running in debugging mode

Stopping at breakpoint

Examining the call stack

Navigating main parameters

Stepping to next statement (F8)

Stepping to next statement

Variable values

Stepping Over

Stepping Into (F9)

Stepping Out

Resuming normal execution

Program termination

Starting Eclipse

Specifying Projects Directory

No Projects Screen

Adding a New Project

Selecting Java Project

Entering Project Name

Switching to Java Perspective

Empty Project

Adding a Package (Optional Step)

Entering Package Name

Workspace, Project, Package  Folder Worskspace Project Package

Adding a New Class File

Naming the File.java suffix needed!

Empty File

Getting Rid of Welcome Pane

Editing the File

Saving the File

Running the Main Method

Output in Console Window Console

Running Main with Parameters

Setting Run Configuration

Run Configuration

Arguments Tab

Executing Debug

Setting a Break Point Double click where you want program to stop

Executing Debug

Starting the Debugger

Stopping at Breakpoint Debug Perspective Next statement to be executed

Examining Main Parameters Main Parameters

Stepping to next statement

Next Statement

New Output and Local Variable Index gets initialized println() executed

Step Over

Step Into Call stack Called method parameters

Step Return

Resume

Returning to Java Perspective

AReverseUpperCasePrinter

No bold face! No Outline!

Deleting File Will also delete from file system

Renaming

Adding.java suffix

Renamed File No bold face! No Outline!

Downloading ObjectEditor Software

Installing ObjectEditor Software

Must do this for each project!

Installing ObjectEditor Software

Testing ObjectEditor Software Any object instance!

Testing ObjectEditor Graphics

Adding a library in JBuilder

Location of All Libraries Use Internet explorer (not Netscape) to download files Latest library names –oe8.jar –shapes3.jar oe8.jar version 8 of oe.jar Sotware may have lots of bugs! Send me mail for workarounds bugs.

The end The rest are extra slides

Previous Main.class shown

Running Another Program with Parameters

Resume