Java Idioms

This is the first draft of what I'll be presenting at DevNexus in February.

Transcript

1. @jeanneboyarsky 1
   Java Idioms
   Jeanne Boyarsky
   Wednesday February 19, 2020
   DevNexus
   speakerdeck.com/boyarsky
   

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2. @jeanneboyarsky
   About Me
   • Java Champion
   • Author
   • Developer at
   NYC bank for
   17+ years
   • FIRST Robotics
   Mentor
   2
   

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3. @jeanneboyarsky
   Pause for a Commercial
   3
   Java 11 certs
   •1Z0-815 - Out now
   •1Z0-816 - April ETA
   

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4. @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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5. @jeanneboyarsky
   Introductions
   5
   

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6. @jeanneboyarsky
   Agenda
   • Strings
   • Regular Expressions
   • Collections
   • Streams
   • Advanced Streams
   • File I/O
   • Other Useful APIs
   6
   

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7. @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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8. @jeanneboyarsky
   Idiom
   • Recurring construct
   • Has meaning
   • Common approach
   8
   

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9. @jeanneboyarsky
   Design Patterns
   • Typically higher level
   • May be language agnostic
   9
   

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10. @jeanneboyarsky
    Anti-Pattern
    • Common “solution”
    • Negative effects
    10
    

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11. @jeanneboyarsky
    Example #1 - What is it?
    11
    Design Pattern
    (Singleton)
    

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12. @jeanneboyarsky
    Example #2 - What is it?
    12
    Idiom
    (Pre-Java 8)
    

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

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14. @jeanneboyarsky
    Example #4 - What is it?
    14
    

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15. @jeanneboyarsky
    Agenda
    • Strings
    • Regular Expressions
    • Collections
    • Streams
    • Advanced Streams
    • File I/O
    • Other Useful APIs
    15
    

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16. @jeanneboyarsky
    Is there a match?
    16
    IntelliJ warning!
    

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17. @jeanneboyarsky 17
    Is there a match?
    

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18. @jeanneboyarsky
    Only whitespace
    18
    

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19. @jeanneboyarsky
    Even Better
    19
    Java 11
    Java 11
    

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20. @jeanneboyarsky
    String Concatentation
    20
    Best choice
    changes over time
    

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21. @jeanneboyarsky
    Equal?
    21
    

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22. @jeanneboyarsky
    Case Insensitive Equal
    22
    

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23. @jeanneboyarsky
    Case Insensitive Compare
    23
    

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24. @jeanneboyarsky
    Creating Csv
    24
    Better to use
    Commons
    CSV Library
    

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25. @jeanneboyarsky
    Multiples
    25
    

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26. @jeanneboyarsky
    How do I unit test this?
    26
    can
    edit?
    pass in a
    mock
    stub out real
    System.out
    Yes
    No
    

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27. @jeanneboyarsky
    Pass Mock object
    27
    

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28. @jeanneboyarsky
    And Test
    28
    

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29. @jeanneboyarsky
    If Cannot Change
    29
    

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

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31. @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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32. @jeanneboyarsky
    Lab
    32
    Do NOT use streams or lambdas
    in this lab
    

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33. @jeanneboyarsky
    Lab & Break
    33
    https://github.com/boyarsky/2020-
    devnexus-java-idioms
    

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34. @jeanneboyarsky
    Agenda
    • Strings
    • Regular Expressions
    • Collections
    • Streams
    • Advanced Streams
    • File I/O
    • Other Useful APIs
    34
    

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35. @jeanneboyarsky
    Lab Review
    • Any questions?
    • How did you solve Tic Tac Toe?
    35
    

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36. @jeanneboyarsky
    Remove all Numbers
    36
    Note replaceAll
    What are two ways to remove
    blanks spaces too?
    

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37. @jeanneboyarsky
    Remove leading pattern
    37
    Three changes:
    replaceFirst()
    ^
    +
    

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38. @jeanneboyarsky
    Remove trailing pattern
    38
    Watch escaping
    

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39. @jeanneboyarsky
    Remove middle
    39
    Off by one error?
    

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40. @jeanneboyarsky
    Ugly regex
    40
    

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41. @jeanneboyarsky
    Better regex
    41
    

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42. @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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43. @jeanneboyarsky
    Splitting on a Regex
    43
    

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44. @jeanneboyarsky
    Contains only digits
    44
    

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45. @jeanneboyarsky
    Contains any digits
    45
    More to regex
    

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46. @jeanneboyarsky
    Case Insensitive
    46
    

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47. @jeanneboyarsky
    Case Insensitive
    47
    

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48. @jeanneboyarsky
    Multi Line Replace
    48
    (?m)
    Also $1
    a
    b
    c
    

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49. @jeanneboyarsky
    Dot All
    49
    (?s)
    
    
    
    
    

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50. @jeanneboyarsky
    Pattern Idiom
    50
    

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51. @jeanneboyarsky
    Pattern Replace
    51
    

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52. @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?
    52
    

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53. @jeanneboyarsky
    Lab & Break
    53
    https://github.com/boyarsky/2020-
    devnexus-java-idioms
    

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54. @jeanneboyarsky
    Agenda
    • Strings
    • Regular Expressions
    • Collections
    • Streams
    • Advanced Streams
    • File I/O
    • Other Useful APIs
    54
    

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55. @jeanneboyarsky
    Lab Review
    • Any questions?
    • Did you like replaceAll() or
    Pattern better?
    • What was hardest?
    55
    

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56. @jeanneboyarsky
    Create a Set
    56
    Java 9
    

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57. @jeanneboyarsky
    Create a List
    57
    Java 9
    

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58. @jeanneboyarsky
    Mutable List
    58
    Java 9
    

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59. @jeanneboyarsky
    Mutable Copy
    59
    

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60. @jeanneboyarsky
    Immutable Copy
    60
    Java 10
    

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61. @jeanneboyarsky
    Synchronized View
    61
    

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62. @jeanneboyarsky
    Unmodifiable View
    62
    

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63. @jeanneboyarsky
    Create a Map
    63
    

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64. @jeanneboyarsky
    Create a Map
    64
    Java 9
    

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65. @jeanneboyarsky
    Sorting
    65
    

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66. @jeanneboyarsky
    Sorting
    66
    

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67. @jeanneboyarsky
    Removing from a List
    67
    

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68. @jeanneboyarsky
    Element in List
    68
    

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69. @jeanneboyarsky
    Replacing
    69
    

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70. @jeanneboyarsky
    Venn Diagram?
    70
    

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71. @jeanneboyarsky
    Defaulting
    71
    

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72. @jeanneboyarsky
    Add to map if not present
    72
    

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73. @jeanneboyarsky
    Other Useful Map Methods
    • containsKey(), containsValue()
    • entrySet()
    • keySet(), values()
    • remove(key)
    • remove(key, value)
    • replace(key, value)
    • replace(key, oldValue, newValue)
    73
    

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74. @jeanneboyarsky
    Printing
    74
    

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75. @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
    75
    

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76. @jeanneboyarsky
    Lab & Break
    76
    https://github.com/boyarsky/2020-
    devnexus-java-idioms
    

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77. @jeanneboyarsky
    Agenda
    • Strings
    • Regular Expressions
    • Collections
    • Streams
    • Advanced Streams
    • File I/O
    • Other Useful APIs
    77
    

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78. @jeanneboyarsky
    Lab Review
    • Did you get them all?
    • Which was your longest
    solution?
    • How many ways did you get the
    challenge question?
    78
    

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79. @jeanneboyarsky
    Optional
    79
    Optional.empty() Optional.of(95)
    95
    

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80. @jeanneboyarsky
    Stream Flow
    80
    Intermediate
    Operations
    Source Terminal Operation
    

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81. @jeanneboyarsky
    Painting Example
    81
    1 2 3
    4 5
    6
    Take sign
    out of box
    Put sign
    in pile
    Intermediate
    Operations
    Paint sign
    

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82. @jeanneboyarsky
    Painting Example
    82
    Take sign
    out of box
    Put sign
    in pile
    Intermediate
    Operations
    Only do 2 signs
    Paint sign
    

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83. @jeanneboyarsky
    Painting Example
    83
    stream() forEach()
    Intermediate
    Operations
    filter() limit()
    sorted()
    

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84. @jeanneboyarsky
    Basic Stream
    84
    

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85. @jeanneboyarsky
    Find max
    85
    

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86. @jeanneboyarsky
    Join a String
    86
    

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87. @jeanneboyarsky
    Get First Elements
    87
    Java 9
    

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88. @jeanneboyarsky
    Get element
    88
    Java 9
    

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89. @jeanneboyarsky
    Strings
    89
    

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90. @jeanneboyarsky
    Useful Terminal Operations
    • count()
    • collect() - more on this next module
    • allMatch(), anyMatch(), noneMatch()
    • findFirst(), findAny()
    • min()/max()
    • forEach()
    90
    

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91. @jeanneboyarsky
    Useful Intermediate Operations
    • filter()
    • map()
    • distinct()
    • limit(), skip()
    • sorted()
    • peek()
    91
    

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92. @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?
    92
    

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93. @jeanneboyarsky
    Lab & Break
    93
    https://github.com/boyarsky/2020-
    devnexus-java-idioms
    

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94. @jeanneboyarsky
    Agenda
    • Strings
    • Regular Expressions
    • Collections
    • Streams
    • Advanced Streams
    • File I/O
    • Other Useful APIs
    94
    

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95. @jeanneboyarsky
    Lab Review
    • Did you get them all?
    • Which was your longest
    solution?
    • What did you come up with for
    takeWhile() or dropWhile()?
    95
    

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96. @jeanneboyarsky
    Infinite: Generating
    96
    

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97. @jeanneboyarsky
    Infinite: Iterative
    97
    Java 9
    

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98. @jeanneboyarsky
    FlatMap
    98
    

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99. @jeanneboyarsky
    Creating Map
    99
    

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100. @jeanneboyarsky
     Creating Map With Conflict
     100
     

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101. @jeanneboyarsky
     Grouping By Key
     101
     

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102. @jeanneboyarsky
     Partitioning By Key
     102
     

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103. @jeanneboyarsky
     Grouping By Key
     103
     

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104. @jeanneboyarsky
     Reduce
     104
     

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105. @jeanneboyarsky
     Review
     • Sources
     • generate()
     • iterate()
     • Intermediate
     • flatMap()
     • Terminal
     • reduce()
     • Collectors
     • toMap()
     • groupingBy()
     • partitioningBy()
     105
     

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106. @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?
     106
     

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107. @jeanneboyarsky
     Lab & Break
     107
     https://github.com/boyarsky/2020-
     devnexus-java-idioms
     

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108. @jeanneboyarsky
     Agenda
     • Strings
     • Regular Expressions
     • Collections
     • Streams
     • Advanced Streams
     • File I/O
     • Other Useful APIs
     108
     

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109. @jeanneboyarsky
     Lab Review
     • Did you get them all?
     • How did you solve the challenge
     problem?
     • Did you see how different
     methods are useful for
     different problems?
     109
     

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110. @jeanneboyarsky
     Creating a Path
     110
     

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111. @jeanneboyarsky
     Absolute Path
     111
     

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112. @jeanneboyarsky
     Separators
     112
     Windows:
     \\ and ;
     Mac/Linux:
     / and :
     

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113. @jeanneboyarsky
     Read File into String
     113
     Java 11
     

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114. @jeanneboyarsky
     Read File into List
     114
     

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115. @jeanneboyarsky
     Read File with Stream
     115
     

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116. @jeanneboyarsky
     Write File from String
     116
     Java 11
     

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117. @jeanneboyarsky
     Write File from List
     117
     

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118. @jeanneboyarsky
     Append To File
     118
     

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119. @jeanneboyarsky
     Walk Tree
     119
     

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120. @jeanneboyarsky
     Convert to unchecked
     120
     Or
     unchecked
     wrapper
     

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121. @jeanneboyarsky
     Delete File
     121
     

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122. @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?
     122
     

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123. @jeanneboyarsky
     Lab & Break
     123
     https://github.com/boyarsky/2020-
     devnexus-java-idioms
     

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124. @jeanneboyarsky
     Agenda
     • Strings
     • Regular Expressions
     • Collections
     • Streams
     • Advanced Streams
     • File I/O
     • Other Useful APIs
     124
     

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125. @jeanneboyarsky
     Lab Review
     • Did you get them all?
     • How did you solve the challenge
     problem?
     • Which seemed easier - reading
     all lines or lines() for the odd/
     even problem?
     125
     

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126. @jeanneboyarsky
     Math
     126
     

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127. @jeanneboyarsky
     Math
     127
     

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128. @jeanneboyarsky
     Random
     128
     

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129. @jeanneboyarsky
     Random
     129
     

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130. @jeanneboyarsky
     Random
     130
     

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131. @jeanneboyarsky
     Random
     131
     

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132. @jeanneboyarsky
     LocalDate
     132
     

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133. @jeanneboyarsky
     LocalDate
     133
     

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134. @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?
     134
     

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135. @jeanneboyarsky
     Before the last lab:
     Tomorrow 10:20am
     Java: Did you know that?
     + Win a book
     135
     

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136. @jeanneboyarsky
     Lab & Break
     136
     https://github.com/boyarsky/2020-
     devnexus-java-idioms
     

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