何时在 JAVA 中的 glob 语法中使用 **（双星）
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When to use ** (double star) in glob syntax within JAVA
提问by Rollerball
Directly from thisJava Oracle tutorial:
直接来自这个Java Oracle 教程：
Two asterisks, **, works like * but crosses directory boundaries. This syntax is generally used for matching complete paths.
两个星号 ** 的作用与 * 类似，但跨越目录边界。此语法通常用于匹配完整路径。
Could anybody do a real example out of it?
What do they mean with "crosses directory boundary"?
Crossing the directory boundary, I imagine something like checking the file from root to getNameCount()-1.
Again a real example explaining the difference between * and ** in practicewould be great.
有人能举出一个真实的例子吗？“跨目录边界”是什么意思？跨越目录边界，我想像检查文件从 root 到getNameCount()-1. 再一次解释 * 和 ** 在实践中的区别的真实例子会很棒。
采纳答案by Sotirios Delimanolis
The javadoc for FileSystem#getPathMatcher()has some pretty good examples and explanations
javadoc forFileSystem#getPathMatcher()有一些很好的例子和解释
*.java Matches a path that represents a file name ending in .java
*.* Matches file names containing a dot
*.{java,class} Matches file names ending with .java or .class
foo.? Matches file names starting with foo. and a single character extension
/home/*/* Matches /home/gus/data on UNIX platforms
/home/** Matches /home/gus and /home/gus/data on UNIX platforms
C:\* Matches C:\foo and C:\bar on the Windows platform (note that the backslash is escaped; as a string literal in the Java Language the pattern would be "C:\\*")
So /home/**would match /home/gus/data, but /home/*wouldn't.
所以/home/**会匹配/home/gus/data，但/home/*不会。
/home/*is saying every file directly in the /homedirectory.
/home/*是说直接在/home目录中的每个文件。
/home/**is saying every file in any directory inside /home.
/home/**是说里面的任何目录中的每个文件/home。
Example of *vs **. Assuming your current working directory is /Users/username/workspace/myproject, then the following will only match the ./myprojectfile (directory).
的例子*VS **。假设您当前的工作目录是/Users/username/workspace/myproject，那么以下只会匹配./myproject文件（目录）。
PathMatcher pathMatcher = FileSystems.getDefault().getPathMatcher("glob:/Users/username/workspace/*");
Files.walk(Paths.get(".")).forEach((path) -> {
path = path.toAbsolutePath().normalize();
System.out.print("Path: " + path + " ");
if (pathMatcher.matches(path)) {
System.out.print("matched");
}
System.out.println();
});
If you use **, it will match all folders and files within that directory.
如果使用**，它将匹配该目录中的所有文件夹和文件。
