- All Implemented Interfaces:
AnnotatedElement
public class Package extends Object implements AnnotatedElement
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.
- 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. - See Java Virtual Machine Specification:
-
5.3 Creation and Loading
- Since:
- 1.2
- See Also:
-
The JAR File Specification: Package Sealing,
ClassLoader.definePackage(String, String, String, String, String, String, String, URL)
-
Method Summary
Modifier and Type Method Description <A extends Annotation>
AgetAnnotation(Class<A> annotationClass)
Returns this element's annotation for the specified type if such an annotation is present, else null.Annotation[]
getAnnotations()
Returns annotations that are present on this element.<A extends Annotation>
A[]getAnnotationsByType(Class<A> annotationClass)
Returns annotations that are associated with this element.<A extends Annotation>
AgetDeclaredAnnotation(Class<A> annotationClass)
Returns this element's annotation for the specified type if such an annotation is directly present, else null.Annotation[]
getDeclaredAnnotations()
Returns annotations that are directly present on this element.<A extends Annotation>
A[]getDeclaredAnnotationsByType(Class<A> annotationClass)
Returns this element's annotation(s) for the specified type if such annotations are either directly present or indirectly present.String
getImplementationTitle()
Return the title of this package.String
getImplementationVendor()
Returns the vendor that implemented this package,null
is returned if it is not known.String
getImplementationVersion()
Return the version of this implementation.String
getName()
Return the name of this package.static Package
getPackage(String name)
Deprecated.static Package[]
getPackages()
Returns all of thePackage
s defined by the caller's class loader and its ancestors.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
isAnnotationPresent(Class<? extends Annotation> annotationClass)
Returns true if an annotation for the specified type is present on this element, else false.boolean
isCompatibleWith(String desired)
Compare this package's specification version with a desired version.boolean
isSealed()
Returns true if this package is sealed.boolean
isSealed(URL url)
Returns true if this package is sealed with respect to the specified code sourceurl
.String
toString()
Returns the string representation of this Package.
-
Method Details
-
getName
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
-
getSpecificationTitle
Return the title of the specification that this package implements.- Returns:
- the specification title,
null
is returned if it is not known.
-
getSpecificationVersion
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(char)
returnstrue
, e.g. 0, 1, 2, ...
- Returns:
- the specification version,
null
is returned if it is not known.
-
getSpecificationVendor
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.
-
getImplementationTitle
Return the title of this package.- Returns:
- the title of the implementation,
null
is returned if it is not known.
-
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:
- the version of the implementation,
null
is returned if it is not known.
-
getImplementationVendor
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.
-
isSealed
public boolean isSealed()Returns true if this package is sealed.- Returns:
- true if the package is sealed, false otherwise
-
isSealed
Returns true if this package is sealed with respect to the specified code sourceurl
.- Parameters:
url
- the code source URL- Returns:
- true if this package is sealed with respect to the given
url
-
isCompatibleWith
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
- the version string of the desired version.- Returns:
- true if this package's version number is greater than or equal to the desired version number
- Throws:
NumberFormatException
- if the current version is not known or the desired or current version is not of the correct dotted form.
-
getPackage
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 ofgetPackage
to return aPackage
from a parent loader, then the properties exposed by thePackage
may not be as expected in the rest of the program. For example, thePackage
will only expose annotations from thepackage-info.class
file defined by the parent loader, even if annotations exist in apackage-info.class
file defined by a child loader. A more robust approach is to use theClassLoader.getDefinedPackage(java.lang.String)
method which returns aPackage
for the specified class loader.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, thePackage
is returned. Otherwise, the ancestors of the caller's class loader are searched recursively (parent by parent) for aPackage
of the given name.Calling this method is equivalent to calling
ClassLoader.getPackage(java.lang.String)
on aClassLoader
instance which is the caller's class loader.- Parameters:
name
- A package name, such as "java.lang
".- Returns:
- The
Package
of the given name defined by the caller's class loader or its ancestors, ornull
if not found. - Throws:
NullPointerException
- ifname
isnull
.- See Also:
ClassLoader.getDefinedPackage(java.lang.String)
-
getPackages
Returns all of thePackage
s defined by the caller's class loader and its ancestors. The returned array may contain more than onePackage
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 aClassLoader
instance which is the caller's class loader.- Returns:
- The array of
Package
objects defined by this class loader and its ancestors - See Also:
ClassLoader.getDefinedPackages()
-
hashCode
public int hashCode()Return the hash code computed from the package name.- Overrides:
hashCode
in classObject
- Returns:
- the hash code computed from the package name.
- See Also:
Object.equals(java.lang.Object)
,System.identityHashCode(java.lang.Object)
-
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. -
getAnnotation
Returns this element's annotation for the specified type if such an annotation is present, else null.Note that any annotation returned by this method is a declaration annotation.
- Specified by:
getAnnotation
in interfaceAnnotatedElement
- Type Parameters:
A
- the type of the annotation to query for and return if present- Parameters:
annotationClass
- the Class object corresponding to the annotation type- Returns:
- this element's annotation for the specified annotation type if present on this element, else null
- Throws:
NullPointerException
- if the given annotation class is null- Since:
- 1.5
-
isAnnotationPresent
Returns true if an annotation for the specified type is present on this element, else false. This method is designed primarily for convenient access to marker annotations.The truth value returned by this method is equivalent to:
getAnnotation(annotationClass) != null
- Specified by:
isAnnotationPresent
in interfaceAnnotatedElement
- Parameters:
annotationClass
- the Class object corresponding to the annotation type- Returns:
- true if an annotation for the specified annotation type is present on this element, else false
- Throws:
NullPointerException
- if the given annotation class is null- Since:
- 1.5
-
getAnnotationsByType
Returns annotations that are associated with this element. If there are no annotations associated with this element, the return value is an array of length 0. The difference between this method andAnnotatedElement.getAnnotation(Class)
is that this method detects if its argument is a repeatable annotation type (JLS 9.6), and if so, attempts to find one or more annotations of that type by "looking through" a container annotation. The caller of this method is free to modify the returned array; it will have no effect on the arrays returned to other callers.Note that any annotations returned by this method are declaration annotations.
- Specified by:
getAnnotationsByType
in interfaceAnnotatedElement
- Type Parameters:
A
- the type of the annotation to query for and return if present- Parameters:
annotationClass
- the Class object corresponding to the annotation type- Returns:
- all this element's annotations for the specified annotation type if associated with this element, else an array of length zero
- Throws:
NullPointerException
- if the given annotation class is null- Since:
- 1.8
-
getAnnotations
Returns annotations that are present on this element. If there are no annotations present on this element, the return value is an array of length 0. The caller of this method is free to modify the returned array; it will have no effect on the arrays returned to other callers.Note that any annotations returned by this method are declaration annotations.
- Specified by:
getAnnotations
in interfaceAnnotatedElement
- Returns:
- annotations present on this element
- Since:
- 1.5
-
getDeclaredAnnotation
Returns this element's annotation for the specified type if such an annotation is directly present, else null. This method ignores inherited annotations. (Returns null if no annotations are directly present on this element.)Note that any annotation returned by this method is a declaration annotation.
- Specified by:
getDeclaredAnnotation
in interfaceAnnotatedElement
- Type Parameters:
A
- the type of the annotation to query for and return if directly present- Parameters:
annotationClass
- the Class object corresponding to the annotation type- Returns:
- this element's annotation for the specified annotation type if directly present on this element, else null
- Throws:
NullPointerException
- if the given annotation class is null- Since:
- 1.8
-
getDeclaredAnnotationsByType
Description copied from interface:AnnotatedElement
Returns this element's annotation(s) for the specified type if such annotations are either directly present or indirectly present. This method ignores inherited annotations. If there are no specified annotations directly or indirectly present on this element, the return value is an array of length 0. The difference between this method andAnnotatedElement.getDeclaredAnnotation(Class)
is that this method detects if its argument is a repeatable annotation type (JLS 9.6), and if so, attempts to find one or more annotations of that type by "looking through" a container annotation if one is present. The caller of this method is free to modify the returned array; it will have no effect on the arrays returned to other callers.- Specified by:
getDeclaredAnnotationsByType
in interfaceAnnotatedElement
- Type Parameters:
A
- the type of the annotation to query for and return if directly or indirectly present- Parameters:
annotationClass
- the Class object corresponding to the annotation type- Returns:
- all this element's annotations for the specified annotation type if directly or indirectly present on this element, else an array of length zero
- Throws:
NullPointerException
- if the given annotation class is null- Since:
- 1.8
-
getDeclaredAnnotations
Returns annotations that are directly present on this element. This method ignores inherited annotations. If there are no annotations directly present on this element, the return value is an array of length 0. The caller of this method is free to modify the returned array; it will have no effect on the arrays returned to other callers.Note that any annotations returned by this method are declaration annotations.
- Specified by:
getDeclaredAnnotations
in interfaceAnnotatedElement
- Returns:
- annotations directly present on this element
- Since:
- 1.5
-
getPackage
to return aPackage
from a parent loader, then the properties exposed by thePackage
may not be as expected in the rest of the program.