Java Idioms for becoming a more powerful developer

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky 1 Java Idioms Jeanne Boyarsky Wednesday June 21, 2023 KCDC speakerdeck.com/boyarsky

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky About Me • Java Champion • Author • Developer at NYC bank for 21+ years • FIRST Robotics Mentor 2

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Pause for a Commercial 3 Java certs: 8/11/17 Book giveaway at end!

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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

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Introductions 5

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Agenda • Strings and Text Blocks • Regular Expressions • Collections & Streams • File I/O + Other Useful APIs 6

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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

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Idiom • Recurring construct • Has meaning • Common approach 8

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Design Patterns • Typically higher level • May be language agnostic 9

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Anti-Pattern • Common “solution” • Negative effects 10

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Example #1 - What is it? 11 Design Pattern (Singleton)

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Example #2 - What is it? 12 Idiom (Pre-Java 8)

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Example #3 - What is it? 13 Anti-pattern * catches “Exception” * ignores exception

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Example #4 - What is it? 14

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Agenda • Strings and Text Blocks • Regular Expressions • Collections & Streams • File I/O + Other Useful APIs 15

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Is there a match? 16 IntelliJ warning!

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky 17 Is there a match?

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Only whitespace 18

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Even Better 19 Java 11 Java 11

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky String Concatentation 20 Best choice changes over time

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Equal? 21

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Case Insensitive Equal 22

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Case Insensitive Compare 23

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Creating Csv 24 Better to use Commons CSV Library

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Multiples 25 Java 11

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Formatting • %s - string • %d - int • %f - float/double (minimum width/precision) • %n - new line

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Formatting Java 15

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@jeanneboyarsky Text Blocks 28 Java 15 (adds line breaks)

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@jeanneboyarsky Text Blocks 29 incidental whitespace essential whitespace no trailing new line quote not escaped

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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

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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

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Lab 32 Do NOT use streams or lambdas in this lab

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Lab & Break 33 https://github.com/boyarsky/ 2023-kcdc-java-idioms

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Agenda • Strings and Text Blocks • Regular Expressions • Collections & Streams • File I/O + Other Useful APIs 34

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Lab Review • Any questions? • How did you solve Tic Tac Toe? 35

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Remove all Numbers 36 Note replaceAll What are two ways to remove blank spaces too?

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Remove leading pattern 37 Three changes: replaceFirst() ^ +

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Remove trailing pattern 38 Watch escaping

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Remove middle 39 Off by one error?

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Ugly regex 40

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Better regex 41

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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

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Brainstorm 43 How many ways can we match one or more using at most 2 x characters?

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Splitting on a Regex 44

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Contains only digits 45

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Contains any digits 46 More to regex

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Case Insensitive 47

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Case Insensitive 48

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Multi Line Replace 49 (?m) Also $1 a b c

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Dot All 50 (?s)

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Pattern Idiom 51

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Pattern Replace 52

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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

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Lab & Break 54 https://github.com/boyarsky/ 2023-kcdc-java-idioms

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Agenda • Strings and Text Blocks • Regular Expressions • Collections & Streams • File I/O + Other Useful APIs 55

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Lab Review • Any questions? • Did you like replaceAll() or Pattern better? • What was hardest? 56

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Create a Set 57 Java 9

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Create a List 58 Java 9

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Mutable List 59 Java 9

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Mutable Copy 60

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Immutable Copy 61 Java 10

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Synchronized View 62

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Unmodifiable View 63

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Create a Map 64

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Create a Map 65 Java 9

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Sorting 66

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Sorting 67

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Removing from a List 68

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Element in List 69

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Replacing 70

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Venn Diagram? 71

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Defaulting 72

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Add to map if not present 73

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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

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Printing 75

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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

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Find max 77

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Join a String 78

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Get First Elements 79 Java 9 and 16

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Get element 80 Java 9

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Strings 81

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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

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Useful Intermediate Operations • filter() • map() • distinct() • limit(), skip() • sorted() • peek() 83

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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

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Infinite: Generating 85

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Infinite: Iterative 86 Java 9

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky FlatMap 87

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Creating Map 88

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Creating Map With Conflict 89

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Grouping By Key 90

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Partitioning By Key 91

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Grouping By Key 92

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Reduce 93

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Review • Sources • generate() • iterate() • Intermediate • flatMap() • Terminal • reduce() • Collectors • toMap() • groupingBy() • partitioningBy() 94

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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

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Lab & Break 96 https://github.com/boyarsky/ 2023-kcdc-java-idioms

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Agenda • Strings and Text Blocks • Regular Expressions • Collections & Streams • File I/O + Other Useful APIs 97

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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

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@jeanneboyarsky Records 99 Java 16 Ran out of room on the screen

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@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)

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Creating a Path 101

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Absolute Path 102

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Separators 103 Windows: \\ and ; Mac/Linux: / and :

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Read File into String 104 Java 11

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Read File into List 105

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Read File with Stream 106

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Write File from String 107 Java 11

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Write File from List 108

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Append To File 109

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Walk Tree 110

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Convert to unchecked 111 Or unchecked wrapper

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Delete File 112

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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? 113

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Math 114

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Math 115

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Random 116

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Random 117

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Random 118

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Random 119

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky LocalDate 120

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky LocalDate 121

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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

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Win a book 123

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky

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twitter.com/jeanneboyarsky mastodon.social/@jeanneboyarsky Lab & Break 125 https://github.com/boyarsky/ 2023-kcdc-java-idioms