public
class
Package
extends Object
implements
AnnotatedElement
| java.lang.Object | |
| ↳ | java.lang.Package |
Package objects contain version information
about the implementation and specification of a Java package.
This versioning information is retrieved and made available
by the ClassLoader instance that
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 isCompatibleWith
method for details.
Specification version numbers use a syntax that consists of nonnegative 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
isDigit(char)returnstrue, 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 identifiers.
Within each 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.
Public methods | |
|---|---|
<A extends Annotation>
A
|
getAnnotation(Class<A> annotationClass)
|
Annotation[]
|
getAnnotations()
Returns all annotations present on this element. |
<A extends Annotation>
A[]
|
getAnnotationsByType(Class<A> annotationClass)
|
<A extends Annotation>
A
|
getDeclaredAnnotation(Class<A> annotationClass)
|
Annotation[]
|
getDeclaredAnnotations()
Returns all annotations that are directly present on this element. |
<A extends Annotation>
A[]
|
getDeclaredAnnotationsByType(Class<A> annotationClass)
|
String
|
getImplementationTitle()
Return the title of this package. |
String
|
getImplementationVendor()
Returns the name of the organization, vendor or company that provided this implementation. |
String
|
getImplementationVersion()
Return the version of this implementation. |
String
|
getName()
Return the name of this package. |
static
Package
|
getPackage(String name)
Find a package by name in the callers |
static
Package[]
|
getPackages()
Get all the packages currently known for the caller's |
String
|
getSpecificationTitle()
Return the title of the specification that this package implements. |
String
|
getSpecificationVendor()
Return the name of the organization, vendor, or company that owns and maintains the specification of the classes that implement this package. |
String
|
getSpecificationVersion()
Returns the version number of the specification that this package implements. |
int
|
hashCode()
Return the hash code computed from the package name. |
boolean
|
isCompatibleWith(String desired)
Compare this package's specification version with a desired version. |
boolean
|
isSealed(URL url)
Returns true if this package is sealed with respect to the specified code source url. |
boolean
|
isSealed()
Returns true if this package is sealed. |
String
|
toString()
Returns the string representation of this Package. |
Inherited methods | |
|---|---|
 From
class
java.lang.Object
| |
From
interface
java.lang.reflect.AnnotatedElement
| |
A getAnnotation (Class<A> annotationClass)
| Parameters | |
|---|---|
annotationClass |
Class
|
| Returns | |
|---|---|
A |
|
| Throws | |
|---|---|
NullPointerException |
|
Annotation[] getAnnotations ()
Returns all annotations present on this element. (Returns an array of length zero if this element has no annotations.) The caller of this method is free to modify the returned array; it will have no effect on the arrays returned to other callers.
| Returns | |
|---|---|
Annotation[] |
all annotations present on this element |
A[] getAnnotationsByType (Class<A> annotationClass)
| Parameters | |
|---|---|
annotationClass |
Class
|
| Returns | |
|---|---|
A[] |
|
| Throws | |
|---|---|
NullPointerException |
|
A getDeclaredAnnotation (Class<A> annotationClass)
| Parameters | |
|---|---|
annotationClass |
Class
|
| Returns | |
|---|---|
A |
|
| Throws | |
|---|---|
NullPointerException |
|
Annotation[] getDeclaredAnnotations ()
Returns all annotations that are directly present on this element. Unlike the other methods in this interface, this method ignores inherited annotations. (Returns an array of length zero if no annotations are directly present on this element.) The caller of this method is free to modify the returned array; it will have no effect on the arrays returned to other callers.
| Returns | |
|---|---|
Annotation[] |
All annotations directly present on this element |
A[] getDeclaredAnnotationsByType (Class<A> annotationClass)
| Parameters | |
|---|---|
annotationClass |
Class
|
| Returns | |
|---|---|
A[] |
|
| Throws | |
|---|---|
NullPointerException |
|
String getImplementationTitle ()
Return the title of this package.
| Returns | |
|---|---|
String |
the title of the implementation, null is returned if it is not known. |
String getImplementationVendor ()
Returns the name of the organization, vendor or company that provided this implementation.
| Returns | |
|---|---|
String |
the vendor that implemented this package.. |
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.
| Returns | |
|---|---|
String |
the version of the implementation, null is returned if it is not known. |
String getName ()
Return the name of this package.
| Returns | |
|---|---|
String |
The fully-qualified name of this package as defined in section 6.5.3 of
The Java™ Language Specification,
for example, java.lang
|
Package getPackage (String name)
Find a package by name in the callers ClassLoader instance.
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
named package.
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.
| Parameters | |
|---|---|
name |
String:
a package name, for example, java.lang. |
| Returns | |
|---|---|
Package |
the package of the requested name. It may be null if no package information is available from the archive or codebase. |
Package[] getPackages ()
Get all the packages currently known for the caller's ClassLoader
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 ClassLoader
instance, which may be represented by null in some implementations,
only packages corresponding to classes loaded by the bootstrap
ClassLoader instance will be returned.
| Returns | |
|---|---|
Package[] |
a new array of packages known to the callers ClassLoader
instance. An zero length array is returned if none are known.
|
String getSpecificationTitle ()
Return the title of the specification that this package implements.
| Returns | |
|---|---|
String |
the specification title, null is returned if it is not known. |
String getSpecificationVendor ()
Return the name of the organization, vendor, or company that owns and maintains the specification of the classes that implement this package.
| Returns | |
|---|---|
String |
the specification vendor, null is returned if it is not known. |
String getSpecificationVersion ()
Returns the version number of the specification that this package implements. This version string must be a sequence of nonnegative decimal integers separated by "."'s and may have leading zeros. When version strings are compared the most significant numbers are compared.
| Returns | |
|---|---|
String |
the specification version, null is returned if it is not known. |
int hashCode ()
Return the hash code computed from the package name.
| Returns | |
|---|---|
int |
the hash code computed from the package name. |
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 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.
| Parameters | |
|---|---|
desired |
String:
the version string of the desired version. |
| Returns | |
|---|---|
boolean |
true if this package's version number is greater than or equal to the desired version number |
| Throws | |
|---|---|
NumberFormatException |
if the desired or current version is not of the correct dotted form. |
boolean isSealed (URL url)
Returns true if this package is sealed with respect to the specified code source url.
| Parameters | |
|---|---|
url |
URL:
the code source url |
| Returns | |
|---|---|
boolean |
true if this package is sealed with respect to url |
boolean isSealed ()
Returns true if this package is sealed.
| Returns | |
|---|---|
boolean |
true if the package is sealed, false otherwise |
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.
| Returns | |
|---|---|
String |
the string representation of the package. |
Developers