Returns a module finder that locates modules on the file system by searching a sequence of directories and/or packaged modules. Each element in the given array is one of:
A path to a directory of modules.
A path to the top-level directory of an exploded module .
A path to a packaged module .
The module finder locates modules by searching each directory, exploded module, or packaged module in array index order. It finds the first occurrence of a module with a given name and ignores other modules of that name that appear later in the sequence.
If an element is a path to a directory of modules then each entry in the directory is a packaged module or the top-level directory of an exploded module. The module finder's
findAll methods throw
FindException if a directory containing more than one module with the same name is encountered.
If an element in the array is a path to a directory, and that directory contains a file named
module-info.class, then the directory is treated as an exploded module rather than a directory of modules.
The module finder returned by this method supports modules that are packaged as JAR files. A JAR file with a
module-info.class in the top-level directory of the JAR file (or overridden by a versioned entry in a
multi-release JAR file) is a modular JAR and is an explicit module . A JAR file that does not have a
module-info.class in the top-level directory is an
automatic module. The
ModuleDescriptor for an automatic module is created as follows:
version if applicable, is derived from the file name of the JAR file as follows:
.jar suffix is removed.
If the name matches the regular expression
"-(\\d+(\\.|$))" then the module name will be derived from the subsequence proceeding the hyphen of the first occurrence. The subsequence after the hyphen is parsed as a
ModuleDescriptor.Version and ignored if it cannot be parsed as a
For the module name, then all non-alphanumeric characters (
[^A-Za-z0-9]) are replaced with a dot (
"."), all repeating dots are replaced with one dot, and all leading and trailing dots are removed.
As an example, a JAR file named
foo-bar.jar will derive a module name
foo.bar and no version. A JAR file named
foo-1.2.3-SNAPSHOT.jar will derive a module name
1.2.3-SNAPSHOT as the version.
All entries in the JAR file with names ending with
.class are assumed to be class files where the name corresponds to the fully qualified name of the class. The packages of all classes are
The contents of all entries starting with
META-INF/services/ are assumed to be service configuration files (see
ServiceLoader). The name of the file (that follows
META-INF/services/) is assumed to be the fully-qualified binary name of a service type. The entries in the file are assumed to be the fully-qualified binary names of provider classes.
If the JAR file has a
Main-Class attribute in its main manifest then its value is the
main class .
In addition to JAR files, an implementation may also support modules that are packaged in other implementation specific module formats. When a file is encountered that is not recognized as a packaged module then
FindException is thrown. An implementation may choose to ignore some files,
hidden files for example. Paths to files that do not exist are always ignored.
As with automatic modules, the contents of a packaged or exploded module may need to be scanned in order to determine the packages in the module. If a
.class file that corresponds to a class in an unnamed package is encountered then
FindException is thrown.
Finders created by this method are lazy and do not eagerly check that the given file paths are directories or packaged modules. Consequently, the
findAll methods will only fail if invoking these methods results in searching a directory or packaged module and an error is encountered. Paths to files that do not exist are ignored.