Java13が出たけどぱっとしないのでJava14を予想する / Java13 new feature and Java14 expectation

2019/10/8に開催されたJavaコミュ＠福岡 勉強会1910での登壇資料です

Transcript

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   #$ !  jshell> s = """ ...> test ...> test ...> """ s ==> "test¥ntest¥n" jshell> s = """ ...> test ...> test ...> """ s ==> " test¥n test¥n" jshell> s = """ ...> test ...> test ...> """ s ==> "test¥n test¥n" jshell> s = """ ...> test ...> test ...> """ s ==> " test¥n test¥n"
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     IntStream.rangeClosed(1, 20) .mapToObj(i -> switch(i % 15) { case 3, 6, 9, 12 -> "Fizz"; case 5,10 -> "Buzz"; case 0 -> "FizzBuzz"; default -> i + ""; }) .map(FizzBuzz::makeStr) .forEach(System.out::print);
6. 3 ( 4 ) ) )3 • 1 2 var result = switch (i % 15) { case 3, 6, 9, 12: yield "Fizz"; case 5, 10: yield "Buzz"; case 0: yield "FizzBuzz"; default: yield i + ""; }
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       • ( D B • ) ( var s = """ select * from %1$s join %2$s on %1$s_id=%2$s_id """.formatted("product", "category"); "from product join category on product_id=category_id"
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    jshell> String s = null s ==> null jshell> s.length() | java.lang.NullPointerException | at (#7:1) jshell> String s = null s ==> null jshell> s.length() | java.lang.NullPointerException | Cannot invoke method ‘length’ because ‘s’ is null | at (#7:1)
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18. ) ( ) ) • ) C • • • ) ( ( record Leaf(int val) {} var l = new Leaf(3); System.out.println(l.val()); System.out.println(l); 3 Leaf[val=3]
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    %! +'#"+/639 ( * $ 5<;7  sealed interface Node permits Branch, Leaf {} record Branch(Node left, Node right) implements Node {} record Leaf(Integer val) implements Node {}
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        static int sum(Node n) { if (n instanceof Branch b) { return sum(b.left()) + sum(b.right()); } else if (n instanceof Leaf l) { return l.val(); } else { return 0; } }
21. ( ) 66 2 1 6 02 3 806 ) 70 8 • E • J static int sum(Node n) { return switch (n) { case Branch b -> sum(b.left()) + sum(b.right()); case Leaf l -> l.val(); } } return switch(n) { case Branch(var l, var r) -> sum(l) + sum(r); case Leaf(var v) -> v; }
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