Scanning

1. Scanning • Scanning image for text. • Scanning frequencies for radio stations. • Finding words in a sentence • Finding identifiers, operators, in a program • char • String • Variable-size type • Indexing • Enumeration

2. Primitive Types • int, double, boolean, long, short, float, byte • char

3. Primitive Types • Constants (Literals & Named Constants) • Operations with Invocation Syntax

4. 16 bits char Escape sequence newline char Constants {letters, digits, operators ...} ‘\n’ ‘a’ ‘1’ ‘’’ ‘\’ ‘ ‘ ‘’ ‘\’’ ‘A‘ ‘< ‘ ‘ ‘\\’

5. Useful Escape Sequences

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

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

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

9. A Useful Character Operation Character.isLetter(c)  true if c is a letter Character.isLetter(‘a’)  true Character.isLetter(‘A’)  true Character.isLetter(‘1’)  false Character.isLetter(‘ ’)  false

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

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

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

13. three different instances Changing Strings? Strings are read-only (immutable) “hello” + “world”  “hello world”

14. Useful String Operations s.toLowerCase()  copy of s with letters converted to lower case s.toUpperCase()  copy of s with letters converted to upper case “Hello World”.toLowerCase()  “hello world” “Hello World”.toUpperCase()  “HELLO WORLD”

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

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

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

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

19. Scanning Problem

20. token token Multi-line input stream Line stream Line 1 Line 2 J o h n F . K e n n e d y token token token Scanning Input stream Token Stream

21. Solution • Monolithic Solution • Class Decomposition

22. Algorithm String inputLine

23. marker 0 Algorithm String inputLine J o h n F . K e n n e d y Output: J

24. Algorithm String inputLine J o h n F . K e n n e d y marker 1 Output: J

25. Algorithm String inputLine J o h n F . K e n n e d y marker 2 Output: J

26. Algorithm String inputLine J o h n F . K e n n e d y marker 5 Output: JF

27. Algorithm String inputLine J o h n F . K e n n e d y marker 6 Output: JF

28. Algorithm String inputLine J o h n F . K e n n e d y marker 8 Output: JFK

29. Algorithm String inputLine J o h n F . K e n n e d y marker 9 Output: JFK

30. Algorithm String inputLine J o h n F . K e n n e d y marker 14 Output: JFK

31. public class UpperCasePrinter { • publicstaticvoid main (String args[]) { • String input = getInput(); • int index = 0; • System.out.println("Upper Case Letters :"); • while (index < input.length()) { • char nextChar = input.charAt(index); • if (Character.isUpperCase(nextChar)) • System.out.print(nextChar); // token processing • index++; • } • } • publicstatic String getInput() { • System.out.println("Please enter a string"); • return Keyboard.readLine(); • } • } Monolithic Solution

32. Storing instead of printing tokens String inputLine J o h n F . K e n n e d y marker 14 String s = “JFK”;

33. No reuse in Monolithic Solutions String s = ""; // token processing int index = 0; while (index < input.length()) { char nextChar = input.charAt(index); if (Character.isUpperCase(nextChar)) s += nextChar; // token processing index++; } int index = 0; System.out.println("Upper Case Letters :");//token processing while (index < input.length()) { char nextChar = input.charAt(index); if (Character.isUpperCase(nextChar)) System.out.print(nextChar); // token processing index++; }

34. Class Decomposition? Main Class

35. Division of Labor in Radio Scanning

36. Division of Labor in Radio Scanning

37. Division of Labor in Radio Scanning

38. Division of Labor in Radio Scanning

39. Division of Labor in Radio Scanning

40. Division of Labor in Radio Scanning

41. Division of Labor in Radio Scanning

42. Division of Labor in Radio Scanning ?

43. Division of Labor in Radio Scanning

44. Class Decomposition instantiate Scanner Class Scanner Object calls Scanner User Main Class (Input & Output)

45. Class Decomposition instantiate DataInputStream Instance DataInputStream readLine() Scanner User Main Class (Input & Output)

46. Scanner User-Scanner Object Interaction • DataInputStream dataIn = new DataInputStream (System.in); • int product = 1; • while (true) { • int num = Integer.parseInt (dataIn.readLine()); • if (num < 0) break; • product = product*num; • } • System.out.println (product);

47. DataInputStream Operations Multi-line input stream Line stream Line 1 Line 2 dataIn.readLine() Line 1 dataIn.readLine() Line 2 dataIn.readLine() IOException

48. Scanner Interface? Input stream Token Stream token 1 token 2 scanner.nextElement() token 1 scanner.nextElement() token 2 scanner.nextElement() ScannerException

49. Scanner Interface? Input stream Token Stream token 1 token 2 scanner.nextElement() token 1 scanner.nextElement() token 2 scanner.hasMoreElements() false scanner.nextElement() ???

50. J o h n F . K e n n e d y token 1 token 2 token 3 Uppercase Scanner Interface? scanner.nextElement() ‘J’ scanner.nextElement() ‘F’ scanner.nextElement() ‘K’ scanner.hasMoreElements() false scanner.nextElement() ???