編集履歴

回答編集履歴

2つ目の方法のコード例を追加

2020/04/22 09:05

投稿

スコア12659

test CHANGED Viewed

@@ -155,3 +155,79 @@
 === OK ===
 ```
+#追加2
+1つ目,2つ目,3つ目...と試す形の場合, 3パターン程度であればあるいは直接並べても良いかもしれませんが, 例えば配列とループにして成功するまで回すという形に出来ます.
+```java
+  private static DateTimeFormatter parsers[] = new DateTimeFormatter[] {
+    DateTimeFormatter.ofPattern("yyyy/MM/dd"),
+    DateTimeFormatter.ofPattern("yyyy-MM-dd"),
+    DateTimeFormatter.ofPattern("yyyyMMdd")
+  };
+  private static LocalDate parse(String str) throws DateTimeParseException {
+    DateTimeParseException ex = null;
+    for(DateTimeFormatter parser : parsers) {
+      try {
+        return LocalDate.parse(str, parser);
+      } catch(DateTimeParseException e) {
+        ex = e;
+      }
+    }
+    throw ex;
+  }
+```
+```plain text
+4567-12-03
+4567-12-03
+4567-12-03
+Text '4567123' could not be parsed at index 6
+Text '456712301' could not be parsed at index 0
+Text '4567-12/30' could not be parsed at index 4
+Text '4567=12=30' could not be parsed at index 4
+Text '4567-12-00' could not be parsed at index 4
+Text '4567-00-30' could not be parsed at index 4
+Text '456-12-30' could not be parsed at index 0
+Text '45678-12-30' could not be parsed at index 4
+Text '' could not be parsed at index 0
+Text 'A-B-C' could not be parsed at index 0
+text
+=== OK ===
+```

追加

2020/04/22 09:05

投稿

jimbe

スコア12659

test CHANGED Viewed

@@ -12,7 +12,7 @@
 #追加
-正規表現で解析するなら, このような感じでしょうか.
+3つ目(?)として正規表現で解析するなら, このような感じでしょうか.
 ```java
@@ -121,3 +121,37 @@
 }
 ```
+```plain text
+4567-12-03
+4567-12-03
+4567-12-03
+unmatch format.
+unmatch format.
+unmatch format.
+unmatch format.
+unmatch format.
+unmatch format.
+unmatch format.
+unmatch format.
+unmatch format.
+unmatch format.
+null
+=== OK ===
+```

追加

2020/04/22 06:56

投稿

jimbe

スコア12659

test CHANGED Viewed

@@ -7,3 +7,117 @@
 もう1つは, 1つ目で変換できなかったら2つ目の変換, 2つ目の変換で変換できなかったら3つ目の変換...と変換できるまで(もしくは変換するフォーマットが無くなるまで)変換を試すことです.
+#追加
+正規表現で解析するなら, このような感じでしょうか.
+```java
+import java.util.*;
+import java.util.regex.*;
+import java.time.*;
+import java.time.format.*;
+public class Main {
+  private static class TestCase {
+    final String str;
+    final boolean result;
+    private TestCase(String str, boolean result) { this.str = str; this.result = result; }
+    static TestCase True(String str) { return new TestCase(str, true); }
+    static TestCase False(String str) { return new TestCase(str, false); }
+  }
+  public static void main(String[] args) throws Exception {
+    TestCase testPattern[] = {
+        TestCase.True("45671203"),TestCase.True("4567/12/03"),TestCase.True("4567-12-03"),
+        TestCase.False("4567123"),TestCase.False("456712301"),
+        TestCase.False("4567-12/30"),TestCase.False("4567=12=30"),TestCase.False("4567-12-00"),
+        TestCase.False("4567-00-30"),TestCase.False("456-12-30"),TestCase.False("45678-12-30"),
+        TestCase.False(""),TestCase.False("A-B-C"),TestCase.False(null),
+    };
+    String totalResult = "=== OK ===";
+    for(TestCase test : testPattern) {
+      if(testParse(test.str) != test.result) totalResult = "*** ERR ***";
+    }
+    System.out.println(totalResult);
+  }
+  private static boolean testParse(String str) {
+    try {
+      LocalDate a = parse(str);
+      System.out.println(a);
+      return true;
+    } catch(Exception e) {
+      System.out.println(e.getMessage());
+      return false;
+    }
+  }
+  private static Pattern DateParsePattern = Pattern.compile("(\d{4})([/-]?)(\d{2})\2(\d{2})");
+  private static LocalDate parse(String str) throws DateTimeParseException {
+    Matcher m = DateParsePattern.matcher(str);
+    if(!m.matches()) throw new DateTimeParseException("unmatch format.", str, -1);
+    try {
+      int year = Integer.parseInt(m.group(1));
+      Month month = Month.of(Integer.parseInt(m.group(3)));
+      int dayOfMonth = Integer.parseInt(m.group(4));
+      return LocalDate.of(year, month, dayOfMonth);
+    } catch(DateTimeException e) {
+      throw new DateTimeParseException("unmatch format.", str, -1, e);
+    }
+  }
+}
+```