如何在Java中与Scanner.useDelimiter一起使用定界符? [英] How do I use a delimiter with Scanner.useDelimiter in Java?

问题描述

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

我不明白定界符是如何工作的，有人可以用外行的方式解释吗?

I don't understand how delimiter works, can someone explain this in layman terms?

推荐答案

扫描仪还可以使用除空格以外的定界符.

The scanner can also use delimiters other than whitespace.

来自 扫描器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(); 

重点是要了解 regex ) ="https://docs.oracle.com/javase/7/docs/api/java/util/Scanner.html#useDelimiter(java.util.regex.Pattern)" rel ="noreferrer"> .在 此处找到useDelimiter教程 .

The point is to understand the regular expressions (regex) inside the Scanner::useDelimiter. Find an useDelimiter tutorial here.

从正则表达式开始 在这里您可以找到 一个很好的教程.

To start with regular expressions here you can find a nice tutorial.

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

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