回答編集履歴
2
最後のラムダ式を他の型にでも使えるよう修正
answer
CHANGED
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@@ -51,7 +51,7 @@
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51
51
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LocalDateTime result = now.with(t -> {
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52
52
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LocalDateTime time = LocalDateTime.from(t);
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53
53
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LocalDateTime r = time.with(LocalTime.of(9, 0));
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54
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-
return r.isBefore(time) ? r.plusDays(1) : r;
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54
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+
return t.with(r.isBefore(time) ? r.plusDays(1) : r);
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55
55
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});
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56
56
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System.out.println(now);
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57
57
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System.out.println(result);
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1
書き方いろいろ
answer
CHANGED
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@@ -6,4 +6,56 @@
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6
6
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if (now.toLocalTime().isAfter(nine))
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7
7
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result = result.plusDays(1);
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8
8
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System.out.println(result);
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9
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+
```
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10
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---
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11
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12
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withの引数にLocalTimeが渡せることに気づいて、いろいろ出てきた。mattnさんのをシンプルに書くと
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13
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+
```java
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14
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import java.time.*;
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15
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16
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public class LT2 {
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17
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public static void main(String[] args) {
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18
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LocalDateTime now = LocalDateTime.now();
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19
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now = now.plusHours(15).with(LocalTime.of(9, 0));
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20
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System.out.println(now);
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21
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}
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22
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}
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23
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```
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24
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私のコードもこうなる
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25
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```java
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26
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import java.time.*;
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27
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+
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28
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public class LT3 {
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29
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public static void main(String[] args) {
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30
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LocalDateTime now = LocalDateTime.now();
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31
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LocalDateTime result = now.with(LocalTime.of(9, 0));
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32
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// 時刻を再設定した結果時間が巻き戻った場合、1日足す
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33
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if (result.isBefore(now)) {
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34
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result = result.plusDays(1);
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35
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}
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36
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System.out.println(result);
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37
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}
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38
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}
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39
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```
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40
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前者がif文もなくすっきり書けるけど、後者は時刻がいつになっても時刻を変えるだけで適用できる。
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41
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42
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ちょっと背伸びして、[TemporalAdjuster](https://docs.oracle.com/javase/jp/8/docs/api/java/time/temporal/TemporalAdjuster.html)をラムダ式で書いてwithメソッドを使ってみた
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43
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```java
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44
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import java.time.LocalDateTime;
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45
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import java.time.LocalTime;
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46
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47
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public class Q81936 {
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48
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49
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public static void main(String[] args) {
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50
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LocalDateTime now = LocalDateTime.now();
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51
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LocalDateTime result = now.with(t -> {
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52
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LocalDateTime time = LocalDateTime.from(t);
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53
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LocalDateTime r = time.with(LocalTime.of(9, 0));
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54
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return r.isBefore(time) ? r.plusDays(1) : r;
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55
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});
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56
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System.out.println(now);
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57
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System.out.println(result);
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58
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}
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59
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60
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}
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9
61
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```
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