2. Object-based Scanning Redo the scanning solution Monolithic, single class solution –does UI and scanning No reuse of code Another scanning problem to show reuse.

3. Scanning Problem

4. Upper case printing 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'); }

5. Printing Scanned Characters Backwards Cannot scan multiple times

6. Strings = Char Sequences JohnF.Kenndye hello String{sequences of characters} 143l0

7. Other Sequences as Predefined Types 100989910090 604050 {sequences of integers} 80 JFKFDR {sequence of Strings} JCBCRRGB 3.83.1 {sequences of doubles} 3.73.13.63.9 IntSequence DoubleSequence StringSequence

8. Other Sequences as Array Types 100989910090 604050 {sequences of integers} 80 {sequence of strings} 3.83.1 {sequences of doubles} 3.73.13.63.9 int[] double[] String[] JFKFDRJCBCRRGB

9. Initializing Array Declarations 10098991009080 int[] assignmentScores = {100, 98, 99, 80}; 3.83.13.73.13.63.9 double[] gpas = {3.8, 3.1, 3.7, 3.1, 3.6, 3.9};String[] initials = {“JFK”, “FDR”, “JC”, “BC”, “GW”, “WW”}; JFKFDRJCBCGWWW assignmentScores Array Type Element Type Array Literal Array Variable

10. Array Operations String[] initials = {“JFK”, “FDR”, “JC”, “BC”, “GW”, “WW”}; JFKFDRJCBCGWWW initials.length  6 initials[0] initials[initials.length - 1] initials[initials.length]  ArrayIndexOutOfBoundsException public named constant initials[0] = “HT” HT initials[initials.length] = “HT”  ArrayIndexOutOfBoundsException Array Instance Size Fixed

11. Array Types have Variable-Size 100989910090 604050 80 int[] 10098991009080 int[] assignmentScores = {100, 98, 99, 100, 99, 80}; assignmentScores assignmentScores = {60, 40, 50}; assignmentScores 604050

12. Uninitializing Array Declaration int[] assignmentScores; assignmentScores null assignmentScores = {60, 40, 50}; assignmentScores 604050

13. Array Elements Uninitialized int[] assignmentScores = new int[3]; assignmentScores 000

14. Printing Scanned Characters Backwards

15. Variable-Size Collection filled part unfilled part current size maximum size

16. 3 J F K sizearray Variable-Size Collection filled part unfilled part current size maximum size

17. Variable-Size Collection static final int MAX_CHARS = 7; static char[] upperCaseLetters = new char [MAX_CHARS]; static int numberOfUpperCaseLetters = 0;

18. Solution package warmup; public class AReverseUpperCasePrinter { static final int MAX_CHARS = 5; static char[] upperCaseLetters = new char[MAX_CHARS]; static int numberOfUpperCaseLetters = 0; public static void main(String[] args){ if (args.length != 1) { System.out.println("Illegal number of arguments:" + args.length + ". Terminating program."); System.exit(-1); } int index = 0; System.out.println("Upper Case Letters:"); while (index < args[0].length()) { if (isUpperCase(args[0].charAt(index))) { System.out.print(args[0].charAt(index)); storeChar(args[0].charAt(index)); } index++; } System.out.println(); printReverse(); }

19. Solution (contd.) public static void storeChar(char c) { if (numberOfUpperCaseLetters == MAX_CHARS) { System.out.println("Too many upper case letters. Terminating program. "); System.exit(-1); } upperCaseLetters[numberOfUpperCaseLetters] = c; numberOfUpperCaseLetters++; } public static void printReverse() { System.out.println("Upper Case Letters in Reverse:"); for (int index =numberOfUpperCaseLetters - 1; index >= 0; index--) { System.out.print(upperCaseLetters[index]); }

20. No reuse in Monolithic Solutions int index = 0; System.out.println("Upper Case Letters :");//token processing while (index < args[0].length()) { if (Character.isUpperCase(args[0].charAt(index);)) { System.out.print(args[0].charAt(index);); // token processing storeChar(args[0].charAt(index)); } index ++; } int index = 0; System.out.println("Upper Case Letters :");//token processing while (index < args[0].length()) { if (Character.isUpperCase(args[0].charAt(index);)) System.out.print(args[0].charAt(index)); // token processing index ++; }

21. Class Decomposition? Main Class

22. Division of Labor in Radio Scanning

29. ?

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

32. BufferedReader Instance readLine() Scanner User Main Class (Input & Output) Class Decomposition BufferedReader instantiate

33. Scanner User-Scanner Object Interaction BufferedReader dataIn = new BufferedReader (new InputStreamReader( System.in)); int product = 1; // add input list terminated by a negative number while (true) { int num = Integer.parseInt (dataIn.readLine()); if (num < 0) break; product = product*num; } System.out.println (product);

34. Constructor parameters InputStreamReader takes System.in as parameter. BufferedReader takes InputStreamReader as parameter. In general, scanner takes object producing scanned stream as parameter.

35. BufferedReader Operations Line 1Line 2 Multi-line input stream Line stream dataIn.readLine()Line 1 dataIn.readLine()Line 2 dataIn.readLine()IOException

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

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

38. Uppercase Scanner Interface? scanner.nextElement()‘J’ scanner.nextElement()‘F’ scanner.hasMoreElements()false JohnF.Kenndye token 1token 2token 3 scanner.nextElement()‘K’ scanner.nextElement()???

39. Enumeration Interfaces package enums; public interface CharEnumeration { public char nextElement(); public boolean hasMoreElements(); } package enums; public interface StringEnumeration { public String nextElement(); public boolean hasMoreElements(); } package ; public interface Enumeration { public nextElement(); public boolean hasMoreElements(); }

40. Using an Enumeration Interface public static void printChars (CharEnumeration charEnumeration) { while (charEnumeration.hasMoreElements()) System.out.print(charEnumeration.nextElement()); } JohnF.Kenndye token 1token 2token 3

41. Using an Enumeration Interface package main; import enums.CharEnumeration; import enums.AnUpperCaseEnumeration; public class UpperCasePrinter { public static void main (String args[]) { if (args.length != 1) { System.out.println("Illegal number of arguments:" + args.length + ". Terminating program."); System.exit(-1); } printUpperCase(args[0]); } public static void printUpperCase(String s) { System.out.println("Upper Case Letters:"); printChars (new AnUpperCaseEnumeration(s)); } public static void printChars (CharEnumeration charEnumeration) { while (charEnumeration.hasMoreElements()) System.out.print(charEnumeration.nextElement()); }

42. Implementing Scanner package enums; public class AnUpperCaseEnumeration implements CharEnumeration { … public AnUpperCaseEnumeration(String theString) {... } public boolean hasMoreElements() {... } public char nextElement() {...; } … }

43. Data Structure: Scanned String package enums; public class AnUpperCaseEnumeration implements CharEnumeration { String string; … public AnUpperCaseEnumeration(String theString) { string = theString;... } public boolean hasMoreElements() {... } public char nextElement() {...; } … }

44. Data Structure: marker JohnF.Kenndye nextElementPos string scanned partUnscanned part nextElementPos is global rather than loop variable

45. hasMoreElements() JohnF.Kenndye string nextElementPos public boolean hasMoreElements() {... } true

46. hasMoreElements() JohnF.Kenndye string nextElementPos public boolean hasMoreElements() {... } true

47. hasMoreElements() JohnF.Kenndye string nextElementPos public boolean hasMoreElements() {... } false

48. hasMoreElements() JohnF.Kenndye string nextElementPos //return true if nextElementPos is beyond end of string; false otherwise public boolean hasMoreElements() {... }

49. hasMoreElements() JohnF.Kenndye string nextElementPos //return false if nextElementPos is beyond end of string; true otherwise public boolean hasMoreElements() { return nextElementPos < string.length(); }

50. nextElement() JohnF.Kenndye string nextElementPos public char nextElement() { }

51. nextElement() JohnF.Kenndye string nextElementPos //Assume nextElemPos is at start of next token or end of string when //method is called. //Method makes sure this is also true before returning. //returns next element if one exists public char nextElements() { }

52. nextElement() JohnF.Kenndye string nextElementPos //Assume nextElemPos is at start of next token or end of string when //method is called. //Method makes sure this is also true before returning. //returns next element if one exists public char nextElement() { } char retVal = string.charAt(nextElemPos) return retVal; while (!isUpperCase(string.charAt(nextElementPos))) nextElemPos++; Unexecuted Loop

53. nextElement() JohnF.Kenndye string nextElementPos //Assume nextElemPos is at start of next token or end of string when //method is called. //Method makes sure this is also true before returning. //returns next element if one exists public char nextElements() { } movePastCurrentToken(); char retVal = extractToken(); return retVal; skipNonTokenCharacters();

54. nextElement() JohnF.Kenndye string nextElementPos //Assume nextElemPos is at start of next token or end of string when //method is called. //returns next token if one exists public char extractToken() { } return string.charAt(nextElementPos);

55. movePastCurrentToken() //Assume nextElemPos is at start of next token or end of string when //method is called. //Moves past current token. public void movePastCurrentToken() { } nextElemPos++; JohnF.Kenndye string nextElementPos

56. skipNonTokenCharacters() JohnF.Kenndye string nextElementPos // keep advancing nextElementPos until we hit the next upper case public void skipNonTokenCharacters() { } while (! isUpperCase(string.charAt(nextElementPos))) nextElemPos++; StringIndexOutOfBounds

57. skipNonTokenCharacters() JohnF.Kenndye string nextElementPos // keep advancing nextElementPos until we hit the next upper case or go // beyond the end of the string. public void skipNonTokenCharacters() { } while (nextElementPos < string.length() && !Character.isUpperCase(string.charAt(nextElement Pos))) nextElemPos++; StringIndexOutOfBounds?short-circuit

58. Initialization johnF.Kenndye string nextElementPos String string; int nextElementPos = 0; public AnUpperCaseEnumeration(String theString) { } string = theString; skipNonTokenCharacters();

59. Complete Scanner package enums; public class AnUpperCaseEnumeration implements CharEnumeration { String string; int nextElementPos = 0; public AnUpperCaseEnumeration(String theString) { string = theString; skipNonTokenCharacters(); } public boolean hasMoreElements() { return nextElementPos < string.length();} public char nextElement() { char retVal = extractToken(); movePastCurrentToken(); skipNonTokenCharacters(); return retVal; } void movePastCurrentToken() {nextElementPos++;} void skipNonTokenCharacters() { while (nextElementPos < string.length() && !isUpperCase(string.charAt(nextElementPos))) nextElementPos++; } char extractToken() { return string.charAt(nextElementPos);} boolean isUpperCase (char c) { return c >= ‘A’ && c <= ‘Z’;} } constructor

60. Scanner Pattern package ; public class implements Enumeration { String string; int nextElementStart = 0; int nextElementEnd = ???; public AnUpperCaseEnumeration(String theString) { string = theString; skipNonTokenCharacters(); } public boolean hasMoreElements() { return nextElementStart < string.length();} public nextElement() { retVal = extractToken(tokenLength); movePastCurrentToken(tokenLength); skipNonTokenCharacters(); return retVal; } void movePastCurrentToken() {…}; void skipNonTokenCharacters() {…}; char extractToken() { …} }

61. AnUpperCaseEnumeration instance Class Decomposition AnUpperCaseEnumeration instantiate AnUppercasePrinter

62. AnUpperCaseEnumeration instance Class Decomposition AnUpperCaseEnumeration instantiate AReverseUpperCasePrinter

63. Reuse of Enumeration while (charEnumeration.hasMoreElements()) { char nextChar = charEnumeration.nextElement()); System.out.print(nextChar); storeChar(nextChar); } while (charEnumeration.hasMoreElements()) System.out.print(charEnumeration.nextElement());

64. Enumeration vs. Scanning public interface CharEnumeration { public char nextElement(); public boolean hasMoreElements(); } JohnF.Kenndye token 1token 2token 3

65. Enumeration without Scanning public interface CharEnumeration { public char nextElement(); public boolean hasMoreElements(); } AllUppercaseLettersInOrder implements ‘A’‘B’...‘Z’

66. Enumerating all Uppercase Letters public boolean hasMoreElements() { ???? } public char nextElement() { ??? } //instance variables ???

67. Enumerating all Uppercase Letters package enumerations; public class AllUpperCaseLettersInOrder implements CharEnumeration { char nextLetter = 'A'; public boolean hasMoreElements() { return nextLetter <= 'Z'; } public char nextElement() { char retVal = nextLetter; nextLetter = (char) (nextLetter + 1); return retVal; }

68. Comparing Two Implementations public interface CharEnumeration { public char nextElement(); public boolean hasMoreElements(); } JohnF.Kenndye token 1token 2token 3 AnUpperCaseEnumeration implements ‘J’‘F’‘K’

69. Radically Different Behaviors public interface CharEnumeration { public char nextElement(); public boolean hasMoreElements(); } AllUppercaseLettersInOrder implements ‘A’‘B’...‘Z’ print (new AnUppercaseEnumeration(s)); print (new AllUppercaseLettersInOrder()); Polymorphism Syntactic Specification!

70. Forward and reverse printing package main; import enums.CharEnumeration; import enums.AnUpperCaseEnumeration; public class AReverseUpperCasePrinter { static final int MAX_CHARS = 5; static char[] upperCaseLetters = new char[MAX_CHARS]; static int numberOfUpperCaseLetters = 0; public static void main(String[] args){ if (args.length != 1) { System.out.println("Illegal number of arguments:" + args.length + ". Terminating program."); System.exit(-1); } printAndStore(args[0]); printReverse(); }

71. Forward and reverse printing public static void printAndStore (String s) { System.out.println("Upper Case Letters:"); printAndStore (new AnUpperCaseEnumeration(s)); } public static void printAndStore (CharEnumeration charEnumeration) { while (charEnumeration.hasMoreElements()) { char inputChar = charEnumeration.nextElement(); System.out.print (inputChar); storeChar(inputChar); } System.out.println(); }

72. Forward and reverse printing (contd.) public static void storeChar(char c) { if (numberOfUpperCaseLetters == MAX_CHARS) { System.out.println("Too many upper case letters. Terminating program. "); System.exit(-1); } upperCaseLetters[numberOfUpperCaseLetters] = c; numberOfUpperCaseLetters++; } public static void printReverse() { System.out.println("Upper Case Letters in Reverse:"); for (int index =numberOfUpperCaseLetters - 1; index >= 0; index--) { System.out.print(upperCaseLetters[index]); }

73. Remaining problems package main; import enums.CharEnumeration; import enums.AnUpperCaseEnumeration; public class AReverseUpperCasePrinter { static final int MAX_CHARS = 5; static char[] upperCaseLetters = new char[MAX_CHARS]; static int numberOfUpperCaseLetters = 0; public static void main(String[] args){ if (args.length != 1) { System.out.println("Illegal number of arguments:" + args.length + ". Terminating program."); System.exit(-1); } printAndStore(args[0]); printReverse(); }

74. Remaining Problems Main class does storing Non UI code Array, size, and max size closely coupled to each other Should be in separate class

75. 3 J F K sizearray Variable-Size Collection filled part unfilled part current size maximum size

76. Variable-Size Collection public class { … final static T A_MAX_SIZE = 50; T[] a = new T [MAX_SIZE]; int aSize = 0; … //process a for (int index = 0; index < aSize; index++) System.out.println(a[index]); … final int B_MAX_SIZE = 50; T[] b = new T [MAX_SIZE]; int bSize = 0; //process b … }

77. Special Type public class {... AVariableSizeTCollection a, b = new AVariableSizeTCollection();... for (int index = 0; index < a.size; index++) System.out.println(a.contents[index]); … AVariableSizeTCollection b = new AVariableSizeTCollection();... } public class AVariableSizeTCollection { public static final int MAX_SIZE = ???; public T[] contents = new T [MAX_SIZE]; public int size = 0; } No encapsulation! a.size = 0; Constraints violated

78. Supporting Encapsulation package collections; public interface …. { public static final int MAX_SIZE = 50; } public void addElement (char element); public void printReverse (); Implementation specific User specific

79. Supporting Encapsulation package collections; public interface CharHistory { } public void addElement (char element); public int size(); public char elementAt (int index);

80. Implementing the History package collections; public class ACharHistory implements CharHistory { public final int MAX_SIZE = 5; char[] contents = new char[MAX_SIZE]; int size = 0; public int size() { return size;} public char elementAt (int index) { return contents[index]; } boolean isFull() { return size == MAX_SIZE; } public void addElement(char element) { if (isFull()) { System.out.println("Adding item to a full history. Terminating program."); System.exit(-1); } else { contents[size] = element; size++; }

81. Using the History package main; import enums.CharEnumeration; import enums.AnUpperCaseEnumeration; import collections.ACharHistory; import collections.CharHistory; public class AModularReverseUpperCasePrinter { static CharHistory upperCaseLetters = new ACharHistory(); public static void main(String[] args) { if (args.length != 1) { System.out.println("Illegal number of arguments:" + args.length + ". Terminating program."); System.exit(-1); } printAndStore(args[0]); printReverse(); }

82. Using the History public static void printAndStore (String s) { System.out.println("Upper Case Letters:"); printAndStore (new AnUpperCaseEnumeration(s)); } public static void printAndStore (CharEnumeration charEnumeration) { while (charEnumeration.hasMoreElements()) { char inputChar = charEnumeration.nextElement(); System.out.print (inputChar); upperCaseLetters.addElement(inputChar); } System.out.println(); }

83. Forward and reverse printing (contd.) public static void printReverse() { System.out.println("Upper Case Letters in Reverse:"); for (int index =upperCaseLetters.size() - 1; index >= 0; index--) { System.out.print(upperCaseLetters.elementAt(index)); }