回答編集履歴
3
追記
test
CHANGED
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@@ -14,4 +14,22 @@
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14
14
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```
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16
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17
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+
異常を伝えるためにもOptionalで返すべきですね。
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18
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19
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```java
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20
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21
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public Optional<Integer> getNum3(Integer num1,Integer num2){
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Optional<Integer> i1 = Optional.ofNullable(num1),
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i2 = Optional.ofNullable(num2);
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return i1.flatMap(x -> i2.map(y -> y - x));
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}
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+
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```
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32
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33
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34
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+
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17
35
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参考→[JavaのOptionalのモナド的な使い方 - 複数のOptional](http://qiita.com/koher/items/6f4a8d8b3ad3142bf645#%E8%A4%87%E6%95%B0%E3%81%AEoptional)
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2
引き算の順番が逆だった
test
CHANGED
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@@ -8,7 +8,7 @@
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8
8
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9
9
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i2 = Optional.ofNullable(num2);
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10
10
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11
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-
return i1.flatMap(x -> i2.map(y ->
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11
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return i1.flatMap(x -> i2.map(y -> y - x)).orElse(0);
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12
12
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}
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14
14
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1
返り値がOptionalのままだった
test
CHANGED
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@@ -8,7 +8,7 @@
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8
8
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9
9
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i2 = Optional.ofNullable(num2);
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10
10
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11
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-
return i1.flatMap(x -> i2.map(y -> x - y));
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11
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+
return i1.flatMap(x -> i2.map(y -> x - y)).orElse(0);
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12
12
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}
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14
14
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