java - 如何在 Java 中使用带有 Scanner.useDelimiter 的分隔符？

Question

sc = new Scanner(new File(dataFile));
sc.useDelimiter(",|\r\n");

我不明白分隔符是如何工作的，有人可以用外行的方式解释一下吗？

Answer 1

The scanner can also use delimiters other than whitespace.

来自Scanner API 的简单示例:

 String input = "1 fish 2 fish red fish blue fish";

 // \\s* means 0 or more repetitions of any whitespace character 
 // fish is the pattern to find
 Scanner s = new Scanner(input).useDelimiter("\\s*fish\\s*");

 System.out.println(s.nextInt());   // prints: 1
 System.out.println(s.nextInt());   // prints: 2
 System.out.println(s.next());      // prints: red
 System.out.println(s.next());      // prints: blue

 // don't forget to close the scanner!!
 s.close(); 

重点是理解regex中的正则表达式(Scanner::useDelimiter) .查找useDelimiter教程here .

---

从正则表达式开始here you can find一个不错的教程。

注意事项

abc…    Letters
123…    Digits
\d      Any Digit
\D      Any Non-digit character
.       Any Character
\.      Period
[abc]   Only a, b, or c
[^abc]  Not a, b, nor c
[a-z]   Characters a to z
[0-9]   Numbers 0 to 9
\w      Any Alphanumeric character
\W      Any Non-alphanumeric character
{m}     m Repetitions
{m,n}   m to n Repetitions
*       Zero or more repetitions
+       One or more repetitions
?       Optional character
\s      Any Whitespace
\S      Any Non-whitespace character
^…$     Starts and ends
(…)     Capture Group
(a(bc)) Capture Sub-group
(.*)    Capture all
(ab|cd) Matches ab or cd