Java Idioms for becoming a more powerful developer

Half day workshop at KCDC: Knowing programming idioms makes us more powerful and faster developers. This session will cover common (and not so common) idioms with regular expressions, file I/O and streams/lambdas. After attending this session, you’ll be able to impress your co-workers with your increased speed in solving programming tasks. You’ll also have the tools to spend less time on the “easy tasks” and more time solving business problems.

Transcript

1. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky 1 Java Idioms Jeanne Boyarsky Wednesday June 21, 2023 KCDC speakerdeck.com/boyarsky
2. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky About Me • Java Champion • Author • Developer at NYC bank for 21+ years • FIRST Robotics Mentor 2
3. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Pause for a Commercial 3 Java certs: 8/11/17 Book giveaway at end!
4. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Disclaimer • A bit of the material is from my books. • Some of the material in this presentation may appear in our upcoming certification books. 4
5. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Introductions 5
6. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Agenda • Strings and Text Blocks • Regular Expressions • Collections & Streams • File I/O + Other Useful APIs 6
7. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Module Flow •Review lab from previous module •Lecture/review •Hands on exercises •10 minute break This means if a colleague needs to call you, the last 15-20 minutes of each hour is best. 7
8. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Idiom • Recurring construct • Has meaning • Common approach 8
9. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Design Patterns • Typically higher level • May be language agnostic 9
10. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Anti-Pattern • Common “solution” • Negative effects 10
11. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Example #1 - What is it? 11 Design Pattern (Singleton)
12. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Example #2 - What is it? 12 Idiom (Pre-Java 8)
13. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Example #3 - What is it? 13 Anti-pattern * catches “Exception” * ignores exception
14. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Example #4 - What is it? 14
15. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Agenda • Strings and Text Blocks • Regular Expressions • Collections & Streams • File I/O + Other Useful APIs 15
16. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Is there a match? 16 IntelliJ warning!
17. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky 17 Is there a match?
18. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Only whitespace 18
19. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Even Better 19 Java 11 Java 11
20. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky String Concatentation 20 Best choice changes over time
21. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Equal? 21
22. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Case Insensitive Equal 22
23. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Case Insensitive Compare 23
24. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Creating Csv 24 Better to use Commons CSV Library
25. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Multiples 25 Java 11
26. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Formatting • %s - string • %d - int • %f - float/double (minimum width/precision) • %n - new line
27. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Formatting Java 15
28. @jeanneboyarsky Text Blocks 28 Java 15 (adds line breaks)
29. @jeanneboyarsky Text Blocks 29 incidental whitespace essential whitespace no trailing new line quote not escaped
30. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Other “new” APIs API Introduced stripLeading() stripTrailing() lines() 11 indent(number) 12 transform(function) 12 stripIndent() translateEscapes() 15 indexOf(ch, beginIndex, endIndex) indexOf(str, beginIndex, endIndex) 21 splitWithDelimiters(regex, limit) 21
31. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Review - What best API? • Check if String empty? • Duplicate String? • Merge Strings? • Compare case sensitive strings? • Compare non-case sensitive strings? 31
32. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Lab 32 Do NOT use streams or lambdas in this lab
33. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Lab & Break 33 https://github.com/boyarsky/ 2023-kcdc-java-idioms
34. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Agenda • Strings and Text Blocks • Regular Expressions • Collections & Streams • File I/O + Other Useful APIs 34
35. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Lab Review • Any questions? • How did you solve Tic Tac Toe? 35
36. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Remove all Numbers 36 Note replaceAll What are two ways to remove blank spaces too?
37. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Remove leading pattern 37 Three changes: replaceFirst() ^ +
38. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Remove trailing pattern 38 Watch escaping
39. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Remove middle 39 Off by one error?
40. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Ugly regex 40
41. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Better regex 41
42. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Regex quick reference 42 0 or more * 1 or more + 0 or 1 ? any . three x’s x{3} range [0-9] Not in range [^0-9] Digit \d White space \s Word \w
43. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Brainstorm 43 How many ways can we match one or more using at most 2 x characters?
44. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Splitting on a Regex 44
45. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Contains only digits 45
46. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Contains any digits 46 More to regex
47. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Case Insensitive 47
48. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Case Insensitive 48
49. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Multi Line Replace 49 (?m) Also $1 a b c
50. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Dot All 50 (?s) <form> <input /> <textarea /> </form>
51. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Pattern Idiom 51
52. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Pattern Replace 52
53. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Review - How do I? • Match digit? • Remove a single match? • Treat dot as any character? • Match a character 100 times? • Loop through matches? • Match a period? 53
54. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Lab & Break 54 https://github.com/boyarsky/ 2023-kcdc-java-idioms
55. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Agenda • Strings and Text Blocks • Regular Expressions • Collections & Streams • File I/O + Other Useful APIs 55
56. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Lab Review • Any questions? • Did you like replaceAll() or Pattern better? • What was hardest? 56
57. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Create a Set 57 Java 9
58. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Create a List 58 Java 9
59. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Mutable List 59 Java 9
60. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Mutable Copy 60
61. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Immutable Copy 61 Java 10
62. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Synchronized View 62
63. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Unmodifiable View 63
64. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Create a Map 64
65. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Create a Map 65 Java 9
66. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Sorting 66
67. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Sorting 67
68. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Removing from a List 68
69. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Element in List 69
70. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Replacing 70
71. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Venn Diagram? 71
72. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Defaulting 72
73. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Add to map if not present 73
74. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Other Useful Map Methods • containsKey(), containsValue() • entrySet() • keySet(), values() • remove(key) • remove(key, value) • replace(key, value) • replace(key, oldValue, newValue) 74
75. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Printing 75
76. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Review - How do I? • Create an immutable copy • Remove all values less than 5 • Update the value in a map if the current value is 10 • Return 0 if the value isn’t found • Find the intersection of two collections 76
77. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Find max 77
78. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Join a String 78
79. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Get First Elements 79 Java 9 and 16
80. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Get element 80 Java 9
81. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Strings 81
82. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Useful Terminal Operations • count() • collect() - more on this next module • allMatch(), anyMatch(), noneMatch() • findFirst(), findAny() • min()/max() • forEach() • toArray, toList() 82
83. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Useful Intermediate Operations • filter() • map() • distinct() • limit(), skip() • sorted() • peek() 83
84. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Review - What method can… • Return whether 5/5 values == 7? • Return whether >=1 values == 7? • Make a stream smaller? • Change the order of stream elements? • Loop through stream elements? • Ignore the first 2 elements? • Ignore any elements are the first 2? 84
85. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Infinite: Generating 85
86. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Infinite: Iterative 86 Java 9
87. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky FlatMap 87
88. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Creating Map 88
89. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Creating Map With Conflict 89
90. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Grouping By Key 90
91. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Partitioning By Key 91
92. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Grouping By Key 92
93. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Reduce 93
94. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Review • Sources • generate() • iterate() • Intermediate • flatMap() • Terminal • reduce() • Collectors • toMap() • groupingBy() • partitioningBy() 94
95. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky What method for? • Creating an infinite stream of a times table? • Creating a Map that always has two keys? • Creating a Map with a custom key/ value? • Returning an Optional representing the stream? 95
96. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Lab & Break 96 https://github.com/boyarsky/ 2023-kcdc-java-idioms
97. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Agenda • Strings and Text Blocks • Regular Expressions • Collections & Streams • File I/O + Other Useful APIs 97
98. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Lab Review • How did you feel about longer streams? • Did you see how different methods are useful for different problems? 98
99. @jeanneboyarsky Records 99 Java 16 Ran out of room on the screen
100. @jeanneboyarsky Records 100 Automatically get * final record * private final instance variables * public accessors * constructor taking both fields * equals * hashCode Can @Override any methods (ex: backward compatibility for getters)
101. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Creating a Path 101
102. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Absolute Path 102
103. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Separators 103 Windows: \\ and ; Mac/Linux: / and :
104. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Read File into String 104 Java 11
105. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Read File into List 105
106. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Read File with Stream 106
107. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Write File from String 107 Java 11
108. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Write File from List 108
109. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Append To File 109
110. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Walk Tree 110
111. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Convert to unchecked 111 Or unchecked wrapper
112. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Delete File 112
113. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky What API to? • Read file into a single string? • Write a List to a file? • Get rid of a file? • List all files in directory? • Add to a file? • Process file as a Stream<String>? 113
114. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Math 114
115. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Math 115
116. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Random 116
117. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Random 117
118. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Random 118
119. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Random 119
120. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky LocalDate 120
121. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky LocalDate 121
122. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky What API to? • Get today? • Get July 4th of this year? • Create a random number between 2 and 10? • Get the largest value of two? • Get a unique id? 122
123. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Win a book 123
124. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky
125. twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Lab & Break 125 https://github.com/boyarsky/ 2023-kcdc-java-idioms