Java 正则表达式不匹配 [英] Java Regex does not match

问题描述

我知道这种问题经常被提出，但是我不明白为什么这个 RegEx 不匹配.我想检查行首是否有M".最后，我想要行尾的路径.这就是 startsWith() 不适合我的需求的原因.

I know that this kind of questions are proposed very often, but I can't figure out why this RegEx does not match. I want to check if there is a "M" at the beginning of the line, or not. Finaly, i want the path at the end of the line. This is why startsWith() doesn't fit my Needs.

line = "M            72208    70779 koj          src\com\company\testproject\TestDomainf1.java";

if (line.matches("^(M?)(.*)$")) {}

我也试过另一种方法:

Pattern p = Pattern.compile("(M?)");
Matcher m = datePatt.matcher(line);
if (m.matches()) {
    System.out.println("yay!");
}

if (line.matches("(M?)(.*)")) {}

谢谢

推荐答案

您不需要正则表达式.只需使用 String#startsWith(String)

You dont need a regex for that. Just use String#startsWith(String)

if (line.startsWith("M")) {
    // code here
}

或者使用 <代码>String#toCharArray():

if (line.length() > 0 && line.toCharArray()[0] == 'M') {
    // code here
}

在您编辑了从输入字符串获取路径的要求之后.

After your edited requirement to get path from input string.

您仍然可以避免使用正则表达式并使用如下代码:

You still can avoid regex and have your code like this:

String path="";
if (line.startsWith("M"))
    path = line.substring(line.lastIndexOf(' ')+1);
System.out.println(path);

输出:

src\com\company\testproject\TestDomainf1.java

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