https://openjdk.java.net/ 
/*
 * Copyright (c) 1997, 2018, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package java.lang;

import java.lang.annotation.Annotation;
import java.lang.reflect.AnnotatedElement;
import java.net.MalformedURLException;
import java.net.URI;
import java.net.URL;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Objects;

import jdk.internal.loader.BootLoader;
import jdk.internal.reflect.CallerSensitive;
import jdk.internal.reflect.Reflection;



Represents metadata about a run-time package associated with a class loader.
Metadata includes annotations, versioning, and sealing.

 Annotations for the run-time package are read from package-info.class at the same code source as classes in the run-time package. 
 The set of classes that make up the run-time package may implement a particular specification. The specification title, version, and vendor (indicating the owner/maintainer of the specification) can be provided when the Package is defined. An application can ask if the Package is compatible with a particular specification version by using the Package.isCompatibleWith(String) method. In addition, information about the actual classes that make up the run-time package can be provided when the Package is defined. This information consists of an implementation title, version, and vendor (indicating the supplier of the classes). 
 A Package may be explicitly defined with the ClassLoader.definePackage(String, String, String, String, String, String, String, URL) method. The caller supplies the specification and implementation titles, versions, and vendors. The caller also indicates whether the package is sealed. If a Package is not explicitly defined for a run-time package when a class in that run-time package is defined, then a Package is automatically defined by the class's defining class loader, as follows. 
 A Package automatically defined for classes in a named module has the following properties: 
    

  • The name of the package is derived from the binary names of the classes. Since classes in a named module must be in a named package, the derived name is never empty.
    • 

  • The package is sealed with the 
    module location as the code source, if known.
    • 

  • The specification and implementation titles, versions, and vendors
    are unspecified.
    • 

  • Any annotations on the package are read from package-info.class as specified above.
    • 



 A Package automatically defined for classes in an unnamed module has the following properties: 
    

  • The name of the package is either "" (for classes in an unnamed package) or derived from the binary names of the classes (for classes in a named package).
    • 

  • The package is not sealed.
    • 

  • The specification and implementation titles, versions, and vendors
    are unspecified.
    • 

  • Any annotations on the package are read from package-info.class as specified above.
    • 



 A Package can be obtained with the 
Package.getPackage(String) and 
ClassLoader.getDefinedPackage(String) methods. Every Package defined by a class loader can be obtained with the Package.getPackages() and ClassLoader.getDefinedPackages methods. 
See Also:
Implementation Note:
The builtin class loaders do not explicitly define Package objects for packages in named modules.  Instead those packages are automatically defined
and have no specification and implementation versioning information.
@jvms5.3 Run-time package
Since:1.2
@revised9
@specJPMS
/**
 * Represents metadata about a run-time package associated with a class loader.
 * Metadata includes annotations, versioning, and sealing.
 * <p>
 * Annotations for the run-time package are read from {@code package-info.class}
 * at the same code source as classes in the run-time package.
 * <p>
 * The set of classes that make up the run-time package may implement a
 * particular specification. The specification title, version, and vendor
 * (indicating the owner/maintainer of the specification) can be provided
 * when the {@code Package} is defined. An application can ask if the
 * {@code Package} is compatible with a particular specification version
 * by using the {@link #isCompatibleWith Package.isCompatibleWith(String)}
 * method. In addition, information about the actual classes that make up the
 * run-time package can be provided when the Package is defined.
 * This information consists of an implementation title, version, and vendor
 * (indicating the supplier of the classes).
 * <p>
 * A {@code Package} may be explicitly defined with
 * the {@link ClassLoader#definePackage(String, String, String, String,
 * String, String, String, URL)} method.
 * The caller supplies the specification and implementation titles, versions, and
 * vendors. The caller also indicates whether the package is
 * {@linkplain java.util.jar.Attributes.Name#SEALED sealed}.
 * If a {@code Package} is not explicitly defined for a run-time package when
 * a class in that run-time package is defined, then a {@code Package} is
 * automatically defined by the class's defining class loader, as follows.
 * <p>
 * A {@code Package} automatically defined for classes in a named module has
 * the following properties:
 * <ul>
 * <li>The name of the package is derived from the {@linkplain Class#getName() binary names}
 *     of the classes. Since classes in a named module must be in a named package,
 *     the derived name is never empty.</li>
 * <li>The package is sealed with the {@linkplain java.lang.module.ModuleReference#location()
 *     module location} as the code source, if known.</li>
 * <li>The specification and implementation titles, versions, and vendors
 *     are unspecified.</li>
 * <li>Any annotations on the package are read from {@code package-info.class}
 *     as specified above.</li>
 * </ul>
 * <p>
 * A {@code Package} automatically defined for classes in an unnamed module
 * has the following properties:
 * <ul>
 * <li>The name of the package is either {@code ""} (for classes in an unnamed package)
 *     or derived from the {@linkplain Class#getName() binary names} of the classes
 *     (for classes in a named package).</li>
 * <li>The package is not sealed.</li>
 * <li>The specification and implementation titles, versions, and vendors
 *     are unspecified.</li>
 * <li>Any annotations on the package are read from {@code package-info.class}
 *     as specified above.</li>
 * </ul>
 *
 * <p>
 * A {@code Package} can be obtained with the {@link Package#getPackage
 * Package.getPackage(String)} and {@link ClassLoader#getDefinedPackage
 * ClassLoader.getDefinedPackage(String)} methods.
 * Every {@code Package} defined by a class loader can be obtained
 * with the {@link Package#getPackages Package.getPackages()} and
 * {@link ClassLoader#getDefinedPackages} methods.
 *
 * @implNote
 * The <a href="ClassLoader.html#builtinLoaders">builtin class loaders</a>
 * do not explicitly define {@code Package} objects for packages in
 * <em>named modules</em>.  Instead those packages are automatically defined
 * and have no specification and implementation versioning information.
 *
 * @jvms 5.3 Run-time package
 * @see <a href="{@docRoot}/../specs/jar/jar.html#package-sealing">
 * The JAR File Specification: Package Sealing</a>
 * @see ClassLoader#definePackage(String, String, String, String, String, String, String, URL)
 *
 * @since 1.2
 * @revised 9
 * @spec JPMS
 */
public class Package extends NamedPackage implements java.lang.reflect.AnnotatedElement {
    
Return the name of this package.

Returns: The fully-qualified name of this package as defined in section 6.5.3 of
         The Java™ Language Specification, for example, java.lang
/**
     * Return the name of this package.
     *
     * @return  The fully-qualified name of this package as defined in section 6.5.3 of
     *          <cite>The Java&trade; Language Specification</cite>,
     *          for example, {@code java.lang}
     */
    public String getName() {
        return packageName();
    }

    
Return the title of the specification that this package implements.

Returns:the specification title, null is returned if it is not known.
/**
     * Return the title of the specification that this package implements.
     * @return the specification title, {@code null} is returned if it is not known.
     */
    public String getSpecificationTitle() {
        return versionInfo.specTitle;
    }

    
Returns the version number of the specification
that this package implements.
This version string must be a sequence of non-negative decimal
integers separated by "."'s and may have leading zeros.
When version strings are compared the most significant
numbers are compared.

Specification version numbers use a syntax that consists of non-negative
decimal integers separated by periods ".", for example "2.0" or
"1.2.3.4.5.6.7".  This allows an extensible number to be used to represent
major, minor, micro, etc. versions.  The version specification is described
by the following formal grammar:





SpecificationVersion:

Digits RefinedVersionopt

RefinedVersion:

. Digits

. Digits RefinedVersion

Digits:

Digit

Digits

Digit:

any character for which Character.isDigit returns true, e.g. 0, 1, 2, ... 




Returns:the specification version, null is returned if it is not known.
/**
     * Returns the version number of the specification
     * that this package implements.
     * This version string must be a sequence of non-negative decimal
     * integers separated by "."'s and may have leading zeros.
     * When version strings are compared the most significant
     * numbers are compared.
     *
     *
     * <p>Specification version numbers use a syntax that consists of non-negative
     * decimal integers separated by periods ".", for example "2.0" or
     * "1.2.3.4.5.6.7".  This allows an extensible number to be used to represent
     * major, minor, micro, etc. versions.  The version specification is described
     * by the following formal grammar:
     * <blockquote>
     * <dl>
     * <dt><i>SpecificationVersion:</i>
     * <dd><i>Digits RefinedVersion<sub>opt</sub></i>

     * <dt><i>RefinedVersion:</i>
     * <dd>{@code .} <i>Digits</i>
     * <dd>{@code .} <i>Digits RefinedVersion</i>
     *
     * <dt><i>Digits:</i>
     * <dd><i>Digit</i>
     * <dd><i>Digits</i>
     *
     * <dt><i>Digit:</i>
     * <dd>any character for which {@link Character#isDigit} returns {@code true},
     * e.g. 0, 1, 2, ...
     * </dl>
     * </blockquote>
     *
     * @return the specification version, {@code null} is returned if it is not known.
     */
    public String getSpecificationVersion() {
        return versionInfo.specVersion;
    }

    
Return the name of the organization, vendor,
or company that owns and maintains the specification
of the classes that implement this package.

Returns:the specification vendor, null is returned if it is not known.
/**
     * Return the name of the organization, vendor,
     * or company that owns and maintains the specification
     * of the classes that implement this package.
     * @return the specification vendor, {@code null} is returned if it is not known.
     */
    public String getSpecificationVendor() {
        return versionInfo.specVendor;
    }

    
Return the title of this package.

Returns:the title of the implementation, null is returned if it is not known.
/**
     * Return the title of this package.
     * @return the title of the implementation, {@code null} is returned if it is not known.
     */
    public String getImplementationTitle() {
        return versionInfo.implTitle;
    }

    
Return the version of this implementation. It consists of any string
assigned by the vendor of this implementation and does
not have any particular syntax specified or expected by the Java
runtime. It may be compared for equality with other
package version strings used for this implementation
by this vendor for this package.

Returns:the version of the implementation, null is returned if it is not known.
/**
     * Return the version of this implementation. It consists of any string
     * assigned by the vendor of this implementation and does
     * not have any particular syntax specified or expected by the Java
     * runtime. It may be compared for equality with other
     * package version strings used for this implementation
     * by this vendor for this package.
     * @return the version of the implementation, {@code null} is returned if it is not known.
     */
    public String getImplementationVersion() {
        return versionInfo.implVersion;
    }

    
Returns the vendor that implemented this package, null is returned if it is not known. 
Returns:the vendor that implemented this package, null is returned if it is not known.
@revised9
@specJPMS
/**
     * Returns the vendor that implemented this package, {@code null}
     * is returned if it is not known.
     * @return the vendor that implemented this package, {@code null}
     * is returned if it is not known.
     *
     * @revised 9
     * @spec JPMS
     */
    public String getImplementationVendor() {
        return versionInfo.implVendor;
    }

    
Returns true if this package is sealed.

Returns:true if the package is sealed, false otherwise
/**
     * Returns true if this package is sealed.
     *
     * @return true if the package is sealed, false otherwise
     */
    public boolean isSealed() {
        return module().isNamed() || versionInfo.sealBase != null;
    }

    
Returns true if this package is sealed with respect to the specified code source url. 
Params:
  • url – the code source URL
Returns:true if this package is sealed with respect to the given url
/**
     * Returns true if this package is sealed with respect to the specified
     * code source {@code url}.
     *
     * @param url the code source URL
     * @return true if this package is sealed with respect to the given {@code url}
     */
    public boolean isSealed(URL url) {
        Objects.requireNonNull(url);

        URL sealBase = null;
        if (versionInfo != VersionInfo.NULL_VERSION_INFO) {
            sealBase = versionInfo.sealBase;
        } else {
            try {
                URI uri = location();
                sealBase = uri != null ? uri.toURL() : null;
            } catch (MalformedURLException e) {
            }
        }
        return url.equals(sealBase);
    }

    
Compare this package's specification version with a
desired version. It returns true if
this packages specification version number is greater than or equal
to the desired version number. 

Version numbers are compared by sequentially comparing corresponding
components of the desired and specification strings.
Each component is converted as a decimal integer and the values
compared.
If the specification value is greater than the desired
value true is returned. If the value is less false is returned.
If the values are equal the period is skipped and the next pair of
components is compared.

Params:
  • desired – the version string of the desired version.
Throws:
  • NumberFormatException – if the current version is not known or
         the desired or current version is not of the correct dotted form.
Returns:true if this package's version number is greater
         than or equal to the desired version number
/**
     * Compare this package's specification version with a
     * desired version. It returns true if
     * this packages specification version number is greater than or equal
     * to the desired version number. <p>
     *
     * Version numbers are compared by sequentially comparing corresponding
     * components of the desired and specification strings.
     * Each component is converted as a decimal integer and the values
     * compared.
     * If the specification value is greater than the desired
     * value true is returned. If the value is less false is returned.
     * If the values are equal the period is skipped and the next pair of
     * components is compared.
     *
     * @param desired the version string of the desired version.
     * @return true if this package's version number is greater
     *          than or equal to the desired version number
     *
     * @exception NumberFormatException if the current version is not known or
     *          the desired or current version is not of the correct dotted form.
     */
    public boolean isCompatibleWith(String desired)
        throws NumberFormatException
    {
        if (versionInfo.specVersion == null || versionInfo.specVersion.length() < 1) {
            throw new NumberFormatException("Empty version string");
        }

        String [] sa = versionInfo.specVersion.split("\\.", -1);
        int [] si = new int[sa.length];
        for (int i = 0; i < sa.length; i++) {
            si[i] = Integer.parseInt(sa[i]);
            if (si[i] < 0)
                throw NumberFormatException.forInputString("" + si[i], 10);
        }

        String [] da = desired.split("\\.", -1);
        int [] di = new int[da.length];
        for (int i = 0; i < da.length; i++) {
            di[i] = Integer.parseInt(da[i]);
            if (di[i] < 0)
                throw NumberFormatException.forInputString("" + di[i], 10);
        }

        int len = Math.max(di.length, si.length);
        for (int i = 0; i < len; i++) {
            int d = (i < di.length ? di[i] : 0);
            int s = (i < si.length ? si[i] : 0);
            if (s < d)
                return false;
            if (s > d)
                return true;
        }
        return true;
    }

    
Finds a package by name in the caller's class loader and its
ancestors.

 If the caller's class loader defines a Package of the given name, the Package is returned. Otherwise, the ancestors of the caller's class loader are searched recursively (parent by parent) for a Package of the given name. 
 Calling this method is equivalent to calling ClassLoader.getPackage on a ClassLoader instance which is the caller's class loader. 
Params:
  • name – A package name, such as "java.lang".
Throws:
See Also:
Returns:The Package of the given name defined by the caller's class loader or its ancestors, or null if not found.
Deprecated: If multiple class loaders delegate to each other and define classes with the same package name, and one such loader relies on the lookup behavior of getPackage to return a Package from a parent loader, then the properties exposed by the Package may not be as expected in the rest of the program. For example, the Package will only expose annotations from the package-info.class file defined by the parent loader, even if annotations exist in a package-info.class file defined by a child loader. A more robust approach is to use the ClassLoader.getDefinedPackage method which returns a Package for the specified class loader.
@revised9
@specJPMS
/**
     * Finds a package by name in the caller's class loader and its
     * ancestors.
     * <p>
     * If the caller's class loader defines a {@code Package} of the given name,
     * the {@code Package} is returned. Otherwise, the ancestors of the
     * caller's class loader are searched recursively (parent by parent)
     * for a {@code Package} of the given name.
     * <p>
     * Calling this method is equivalent to calling {@link ClassLoader#getPackage}
     * on a {@code ClassLoader} instance which is the caller's class loader.
     *
     * @param name A package name, such as "{@code java.lang}".
     * @return The {@code Package} of the given name defined by the caller's
     *         class loader or its ancestors, or {@code null} if not found.
     *
     * @throws NullPointerException
     *         if {@code name} is {@code null}.
     *
     * @deprecated
     * If multiple class loaders delegate to each other and define classes
     * with the same package name, and one such loader relies on the lookup
     * behavior of {@code getPackage} to return a {@code Package} from
     * a parent loader, then the properties exposed by the {@code Package}
     * may not be as expected in the rest of the program.
     * For example, the {@code Package} will only expose annotations from the
     * {@code package-info.class} file defined by the parent loader, even if
     * annotations exist in a {@code package-info.class} file defined by
     * a child loader.  A more robust approach is to use the
     * {@link ClassLoader#getDefinedPackage} method which returns
     * a {@code Package} for the specified class loader.
     *
     * @see ClassLoader#getDefinedPackage
     *
     * @revised 9
     * @spec JPMS
     */
    @CallerSensitive
    @Deprecated(since="9")
    @SuppressWarnings("deprecation")
    public static Package getPackage(String name) {
        ClassLoader l = ClassLoader.getClassLoader(Reflection.getCallerClass());
        return l != null ? l.getPackage(name) : BootLoader.getDefinedPackage(name);
    }

    
Returns all of the Packages defined by the caller's class loader and its ancestors. The returned array may contain more than one Package object of the same package name, each defined by a different class loader in the class loader hierarchy. 
 Calling this method is equivalent to calling ClassLoader.getPackages on a ClassLoader instance which is the caller's class loader. 
See Also:
Returns: The array of Package objects defined by this class loader and its ancestors
@revised9
@specJPMS
/**
     * Returns all of the {@code Package}s defined by the caller's class loader
     * and its ancestors.  The returned array may contain more than one
     * {@code Package} object of the same package name, each defined by
     * a different class loader in the class loader hierarchy.
     * <p>
     * Calling this method is equivalent to calling {@link ClassLoader#getPackages}
     * on a {@code ClassLoader} instance which is the caller's class loader.
     *
     * @return  The array of {@code Package} objects defined by this
     *          class loader and its ancestors
     *
     * @see ClassLoader#getDefinedPackages
     *
     * @revised 9
     * @spec JPMS
     */
    @CallerSensitive
    public static Package[] getPackages() {
        ClassLoader cl = ClassLoader.getClassLoader(Reflection.getCallerClass());
        return cl != null ? cl.getPackages() : BootLoader.packages().toArray(Package[]::new);
    }

    
Return the hash code computed from the package name.

Returns:the hash code computed from the package name.
/**
     * Return the hash code computed from the package name.
     * @return the hash code computed from the package name.
     */
    @Override
    public int hashCode(){
        return packageName().hashCode();
    }

    
Returns the string representation of this Package.
Its value is the string "package " and the package name.
If the package title is defined it is appended.
If the package version is defined it is appended.

Returns:the string representation of the package.
/**
     * Returns the string representation of this Package.
     * Its value is the string "package " and the package name.
     * If the package title is defined it is appended.
     * If the package version is defined it is appended.
     * @return the string representation of the package.
     */
    @Override
    public String toString() {
        String spec = versionInfo.specTitle;
        String ver =  versionInfo.specVersion;
        if (spec != null && !spec.isEmpty())
            spec = ", " + spec;
        else
            spec = "";
        if (ver != null && !ver.isEmpty())
            ver = ", version " + ver;
        else
            ver = "";
        return "package " + packageName() + spec + ver;
    }

    private Class<?> getPackageInfo() {
        if (packageInfo == null) {
            // find package-info.class defined by loader
            String cn = packageName() + ".package-info";
            Module module = module();
            PrivilegedAction<ClassLoader> pa = module::getClassLoader;
            ClassLoader loader = AccessController.doPrivileged(pa);
            Class<?> c;
            if (loader != null) {
                c = loader.loadClass(module, cn);
            } else {
                c = BootLoader.loadClass(module, cn);
            }

            if (c != null) {
                packageInfo = c;
            } else {
                // store a proxy for the package info that has no annotations
                class PackageInfoProxy {}
                packageInfo = PackageInfoProxy.class;
            }
        }
        return packageInfo;
    }

    
Throws:
  • NullPointerException – {@inheritDoc}
Since:1.5
/**
     * @throws NullPointerException {@inheritDoc}
     * @since 1.5
     */
    public <A extends Annotation> A getAnnotation(Class<A> annotationClass) {
        return getPackageInfo().getAnnotation(annotationClass);
    }

    
{@inheritDoc}

Throws:
Since:1.5
/**
     * {@inheritDoc}
     * @throws NullPointerException {@inheritDoc}
     * @since 1.5
     */
    @Override
    public boolean isAnnotationPresent(Class<? extends Annotation> annotationClass) {
        return AnnotatedElement.super.isAnnotationPresent(annotationClass);
    }

    
Throws:
  • NullPointerException – {@inheritDoc}
Since:1.8
/**
     * @throws NullPointerException {@inheritDoc}
     * @since 1.8
     */
    @Override
    public  <A extends Annotation> A[] getAnnotationsByType(Class<A> annotationClass) {
        return getPackageInfo().getAnnotationsByType(annotationClass);
    }

    
Since:1.5
/**
     * @since 1.5
     */
    public Annotation[] getAnnotations() {
        return getPackageInfo().getAnnotations();
    }

    
Throws:
  • NullPointerException – {@inheritDoc}
Since:1.8
/**
     * @throws NullPointerException {@inheritDoc}
     * @since 1.8
     */
    @Override
    public <A extends Annotation> A getDeclaredAnnotation(Class<A> annotationClass) {
        return getPackageInfo().getDeclaredAnnotation(annotationClass);
    }

    
Throws:
  • NullPointerException – {@inheritDoc}
Since:1.8
/**
     * @throws NullPointerException {@inheritDoc}
     * @since 1.8
     */
    @Override
    public <A extends Annotation> A[] getDeclaredAnnotationsByType(Class<A> annotationClass) {
        return getPackageInfo().getDeclaredAnnotationsByType(annotationClass);
    }

    
Since:1.5
/**
     * @since 1.5
     */
    public Annotation[] getDeclaredAnnotations()  {
        return getPackageInfo().getDeclaredAnnotations();
    }

    
Construct a package instance for an unnamed module
with the specified version information.

Params:
  • name – the name of the package
  • spectitle – the title of the specification
  • specversion – the version of the specification
  • specvendor – the organization that maintains the specification
  • impltitle – the title of the implementation
  • implversion – the version of the implementation
  • implvendor – the organization that maintains the implementation
  • sealbase – code source where this Package comes from
  • loader – defining class loader
API Note:
This method should not be called to define a Package for named module.
/**
     * Construct a package instance for an unnamed module
     * with the specified version information.
     *
     * @apiNote
     * This method should not be called to define a Package for named module.
     *
     * @param name the name of the package
     * @param spectitle the title of the specification
     * @param specversion the version of the specification
     * @param specvendor the organization that maintains the specification
     * @param impltitle the title of the implementation
     * @param implversion the version of the implementation
     * @param implvendor the organization that maintains the implementation
     * @param sealbase code source where this Package comes from
     * @param loader defining class loader
     */
    Package(String name,
            String spectitle, String specversion, String specvendor,
            String impltitle, String implversion, String implvendor,
            URL sealbase, ClassLoader loader)
    {
        super(Objects.requireNonNull(name),
              loader != null ? loader.getUnnamedModule()
                             : BootLoader.getUnnamedModule());

        this.versionInfo = VersionInfo.getInstance(spectitle, specversion,
                                                   specvendor, impltitle,
                                                   implversion, implvendor,
                                                   sealbase);
    }

    Package(String name, Module module) {
        super(name, module);
        this.versionInfo = VersionInfo.NULL_VERSION_INFO;
    }

    /*
     * Versioning information.  Only for packages in unnamed modules.
     */
    static class VersionInfo {
        static final VersionInfo NULL_VERSION_INFO
            = new VersionInfo(null, null, null, null, null, null, null);

        private final String specTitle;
        private final String specVersion;
        private final String specVendor;
        private final String implTitle;
        private final String implVersion;
        private final String implVendor;
        private final URL sealBase;

        static VersionInfo getInstance(String spectitle, String specversion,
                                       String specvendor, String impltitle,
                                       String implversion, String implvendor,
                                       URL sealbase) {
            if (spectitle == null && specversion == null &&
                    specvendor == null && impltitle == null &&
                    implversion == null && implvendor == null &&
                    sealbase == null) {
                return NULL_VERSION_INFO;
            }
            return new VersionInfo(spectitle, specversion, specvendor,
                    impltitle, implversion, implvendor,
                    sealbase);
        }

        private VersionInfo(String spectitle, String specversion,
                            String specvendor, String impltitle,
                            String implversion, String implvendor,
                            URL sealbase)
        {
            this.implTitle = impltitle;
            this.implVersion = implversion;
            this.implVendor = implvendor;
            this.specTitle = spectitle;
            this.specVersion = specversion;
            this.specVendor = specvendor;
            this.sealBase = sealbase;
        }
    }

    private final VersionInfo versionInfo;
    private Class<?> packageInfo;
}