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OCPJP708.5
Cert Obj Find a file with PathMatcher interface.
| [8.5.1] Objective | Find a file with PathMatcher interface. |
| [8.5.2] What is a glob? | PathMatchers use a new type that you probably haven't seen before called a glob. Globs are not regular expressions, although they might look similar at first. |
| [8.5.3]In the world of globs, one asterisk means "match any character except for a directory boundary." Two asterisks means "match any character, including a directory boundary." | Path path = Paths.get("/com/java/One.java"); matches(path, "glob:*.java"); // false matches(path, "glob:**/*.java"); // true matches(path, "glob:*"); // false matches(path, "glob:**"); // true |
| [8.5.4] Remember that we are using a file system–specific PathMatcher. This means slashes and backslashes can be treated differently, depending on what operating system you happen to be running. | The previous example does print the same output on both Windows and UNIX because it uses forward slashes. |
| [8.5.5] Unix vs Windows | Path path = Paths.get("com\\java\\One.java"); Now Windows still prints: false true false true However, UNIX prints: true false true true |
| [8.5.6] Preferred | Why? Because UNIX doesn't see the backslash as a directory boundary. The lesson here is to use / instead of \\ so your code behaves more predictably across operating systems. |
| [8.5.7]A question mark matches any character. A character could be a letter or a number or anything else | Path path1 = Paths.get("One.java"); Path path2 = Paths.get("One.ja^a"); matches(path1, "glob:*.????"); // true matches(path1, "glob:*.???"); // false matches(path2, "glob:*.????"); // true matches(path2, "glob:*.???"); // false |
| [8.5.8]Boilerplate code | public void matches(Path path, String glob) { PathMatcher matcher = FileSystems.getDefault().getPathMatcher(glob); System.out.println(matcher.matches(path)); } |
| [8.5.9] More examples | Path path1 = Paths.get("Bert-book"); Path path2 = Paths.get("Kathy-horse"); matches(path1, "glob:{Bert*,Kathy*}"); // true matches(path2, "glob:{Bert,Kathy}*"); // true matches(path1, "glob:{Bert,Kathy}"); // false |
| [8.5.10] More on glob1 (Java won't let you type a single backslash, so you have to escape the backslash itself with another backslash.) | ■ [0-9] One single digit. Can also be read as any one character from 0 to 9. ■ \\* The literal character asterisk rather than the asterisk that means to match anything. A single backslash before * escapes it. |
| [8.5.11] More on glob2 | ■ {A*,b} Either a capital A followed by anything or the single character b. ■ /**/ One or more directories with any name. ■ 1 The single character 1. |
Created by:
MVK2013
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