https://openjdk.java.net/ 
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 * accompanied this code).
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package java.lang.module;

import java.io.IOException;
import java.net.URI;
import java.util.Objects;
import java.util.Optional;



A reference to a module's content.

 A module reference is a concrete implementation of this class that implements the abstract methods defined by this class. It contains the module's descriptor and its location, if known. It also has the ability to create a ModuleReader in order to access the module's content, which may be inside the Java run-time system itself or in an artifact such as a modular JAR file. 
See Also:
Since:9
@specJPMS
/**
 * A reference to a module's content.
 *
 * <p> A module reference is a concrete implementation of this class that
 * implements the abstract methods defined by this class. It contains the
 * module's descriptor and its location, if known.  It also has the ability to
 * create a {@link ModuleReader} in order to access the module's content, which
 * may be inside the Java run-time system itself or in an artifact such as a
 * modular JAR file.
 *
 * @see ModuleFinder
 * @see ModuleReader
 * @since 9
 * @spec JPMS
 */

public abstract class ModuleReference {

    private final ModuleDescriptor descriptor;
    private final URI location;

    
Constructs a new instance of this class.

Params:
  • descriptor – 
       The module descriptor
  • location –  The module location or null if not known
/**
     * Constructs a new instance of this class.
     *
     * @param descriptor
     *        The module descriptor
     * @param location
     *        The module location or {@code null} if not known
     */
    protected ModuleReference(ModuleDescriptor descriptor, URI location) {
        this.descriptor = Objects.requireNonNull(descriptor);
        this.location = location;
    }

    
Returns the module descriptor.

Returns:The module descriptor
/**
     * Returns the module descriptor.
     *
     * @return The module descriptor
     */
    public final ModuleDescriptor descriptor() {
        return descriptor;
    }

    
Returns the location of this module's content, if known.

 This URI, when present, can be used as the location value of a CodeSource so that a module's classes can be granted specific permissions when loaded by a SecureClassLoader. 
Returns:The location or an empty Optional if not known
/**
     * Returns the location of this module's content, if known.
     *
     * <p> This URI, when present, can be used as the {@linkplain
     * java.security.CodeSource#getLocation location} value of a {@link
     * java.security.CodeSource CodeSource} so that a module's classes can be
     * granted specific permissions when loaded by a {@link
     * java.security.SecureClassLoader SecureClassLoader}.
     *
     * @return The location or an empty {@code Optional} if not known
     */
    public final Optional<URI> location() {
        return Optional.ofNullable(location);
    }

    
Opens the module content for reading.

Throws:
Returns:A ModuleReader to read the module
/**
     * Opens the module content for reading.
     *
     * @return A {@code ModuleReader} to read the module
     *
     * @throws IOException
     *         If an I/O error occurs
     * @throws SecurityException
     *         If denied by the security manager
     */
    public abstract ModuleReader open() throws IOException;
}