Glob pattern using getPathMatcher

Question

From the book of "Kathy Sierra Bert Bates" for OCP exam I found the following code

public class FileTest {

    public static void matches(Path path, String glob){
        PathMatcher matcher = FileSystems.getDefault().getPathMatcher(glob);
        System.out.println(matcher.matches(path));
    }
    public static void main(String[] args) throws IOException {
        Path path = Paths.get("/com/java/One.java");
        matches(path, "glob:*.java");
        matches(path, "glob:**/*.java");
        matches(path, "glob:*");
        matches(path, "glob:**");

    }
}

Output:

false
true
false
true

I can not understand the output clearly. Would any one explain me. let me know my example what is crossing directory boundaries. Thanks Rocky

Answer 1

matches(path, "glob:*.java"); // => flase

because your path contains / which describe a directory hierarchy, *.java matches any file name with .java extension

matches(path, "glob:**/*.java"); // => true

because ** matches any string, including sub-path (like /com/java/ in you example)

matches(path, "glob:*"); // => false

as mentioned in the first one, because you have path separator /

matches(path, "glob:**"); // => true

as mentioned in the second one, because ** matches any string including /

Answer 2

public class FileTest {

    public static void matches(Path path, String glob){
        PathMatcher matcher = FileSystems.getDefault().getPathMatcher(glob);
        System.out.println(matcher.matches(path));
    }
    public static void main(String[] args) throws IOException {
        Path path = Paths.get("/com/java/One.java");
        matches(path, "glob:*.java");       // regular expression that matches any file path that end with .java so it will return the value as true
        matches(path, "glob:**/*.java"); // regular expression ** characters matches zero or more characters crossing directory boundaries so it will match complete path but if you put /* it will search for a path like this /com/java//one.java soe here it will not match the path and will return value as false.
        matches(path, "glob:*"); // this will match any path and return value as true.
        matches(path, "glob:**"); // this will complete path crossing directory so it will return you value as true.

    }
}

In the above program when you are calling matches with the path as "/com/java/One.java" and glob regular expression for searching or matching the path the function will take the values and perform the operation and return true or false. Output:

true
false
true
true

If you are using the windows platform then you need to modify your program as follows.

public class match {

  public static void matches(Path path, String glob){
    PathMatcher matcher = FileSystems.getDefault().getPathMatcher(glob);
    System.out.println(matcher.matches(path));
  }
  public static void main(String[] args) throws IOException {
    Path path = Paths.get("\\com\\java\\One.java");
    matches(path, "glob:*.java");
    matches(path, "glob:**\\*.java");
    matches(path, "glob:*");
    matches(path, "glob:**");

  }
}

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