JavaTM 2 Platform Std. Ed. v1.4.2
- public class Package
- extends Object
Package objects contain version information
about the implementation and specification of a Java package.
This versioning information is retrieved and made available
loaded the class(es). Typically, it is stored in the manifest that is
distributed with the classes.
The set of classes that make up the package may implement a
particular specification and if so the specification title, version number,
and vendor strings identify that specification.
An application can ask if the package is
compatible with a particular version, see the
method for details.
Specification version numbers use a syntax that consists of positive
decimal integers separated by periods ".", for example "2.0" or
"220.127.116.11.5.6.7". 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:
- Digits RefinedVersionopt
. Digits RefinedVersion
- any character for which
e.g. 0, 1, 2, ...
The implementation title, version, and vendor strings identify an
implementation and are made available conveniently to enable accurate
reporting of the packages involved when a problem occurs. The contents
all three implementation strings are vendor specific. The
implementation version strings have no specified syntax and should
only be compared for equality with desired version identifers.
ClassLoader instance all classes from the same
java package have the same Package object. The static methods allow a package
to be found by name or the set of all packages known to the current class
loader to be found.
- See Also:
ClassLoader.definePackage(java.lang.String, java.lang.String, java.lang.String, java.lang.String, java.lang.String, java.lang.String, java.lang.String, java.net.URL)
public String getName()
- Return the name of this package.
- The name of this package using the Java language dot notation
for the package. i.e java.lang
public String getSpecificationTitle()
- Return the title of the specification that this package implements.
- the specification title, null is returned if it is not known.
public String getSpecificationVersion()
- Returns the version number of the specification
that this package implements.
This version string must be a sequence of positive decimal
integers separated by "."'s and may have leading zeros.
When version strings are compared the most significant
numbers are compared.
- the specification version, null is returned if it is not known.
public String getSpecificationVendor()
- Return the name of the organization, vendor,
or company that owns and maintains the specification
of the classes that implement this package.
- the specification vendor, null is returned if it is not known.
public String getImplementationTitle()
- Return the title of this package.
- the title of the implementation, null is returned if it is not known.
public String getImplementationVersion()
- 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.
- the version of the implementation, null is returned if it is not known.
public String getImplementationVendor()
- Returns the name of the organization,
vendor or company that provided this implementation.
- the vendor that implemented this package..
public boolean isSealed()
- Returns true if this package is sealed.
- true if the package is sealed, false otherwise
public boolean isSealed(URL url)
- Returns true if this package is sealed with respect to the specified
code source url.
url - the code source url
- true if this package is sealed with respect to url
public boolean isCompatibleWith(String desired)
- 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
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.
desired - the version string of the desired version.
- true if this package's version number is greater
than or equal to the desired version number
NumberFormatException - if the desired or current version
is not of the correct dotted form.
public static Package getPackage(String name)
- Find a package by name in the callers
ClassLoader instance is used to find the package
instance corresponding to the named class. If the callers
ClassLoader instance is null then the set of packages loaded
by the system
ClassLoader instance is searched to find the
Packages have attributes for versions and specifications only if the class
loader created the package instance with the appropriate attributes. Typically,
those attributes are defined in the manifests that accompany the classes.
name - a package name, for example, java.lang.
- the package of the requested name. It may be null if no package
information is available from the archive or codebase.
public static Package getPackages()
- Get all the packages currently known for the caller's
instance. Those packages correspond to classes loaded via or accessible by
name to that
ClassLoader instance. If the caller's
ClassLoader instance is the bootstrap
instance, which may be represented by
null in some implementations,
only packages corresponding to classes loaded by the bootstrap
ClassLoader instance will be returned.
- a new array of packages known to the callers
instance. An zero length array is returned if none are known.
public int hashCode()
- Return the hash code computed from the package name.
hashCode in class
- the hash code computed from the package name.
- See Also:
public String toString()
- 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.
toString in class
- the string representation of the package.
Copyright 2003 Sun Microsystems, Inc. All rights reserved