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Java™ Platform Standard Ed. 6 |
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java.lang.Object java.lang.Package
public class 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
instance that
loaded the class(es). Typically, it is stored in the manifest that is
distributed with the classes.
ClassLoader
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.
isCompatibleWith
Specification version numbers use a syntax that consists of positive 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, ...
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.
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)
Method Summary | ||
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getAnnotation(Class<A> annotationClass)
Returns this element's annotation for the specified type if such an annotation is present, else null. |
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Annotation[] |
getAnnotations()
Returns all annotations present on this element. |
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Annotation[] |
getDeclaredAnnotations()
Returns all annotations that are directly present on this element. |
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String |
getImplementationTitle()
Return the title of this package. |
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String |
getImplementationVendor()
Returns the name of the organization, vendor or company that provided this implementation. |
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String |
getImplementationVersion()
Return the version of this implementation. |
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String |
getName()
Return the name of this package. |
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static Package |
getPackage(String name)
Find a package by name in the callers ClassLoader instance. |
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static Package[] |
getPackages()
Get all the packages currently known for the caller's ClassLoader
instance. |
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String |
getSpecificationTitle()
Return the title of the specification that this package implements. |
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String |
getSpecificationVendor()
Return the name of the organization, vendor, or company that owns and maintains the specification of the classes that implement this package. |
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String |
getSpecificationVersion()
Returns the version number of the specification that this package implements. |
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int |
hashCode()
Return the hash code computed from the package name. |
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boolean |
isAnnotationPresent(Class<? extends Annotation> annotationClass)
Returns true if an annotation for the specified type is present on this element, else false. |
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boolean |
isCompatibleWith(String desired)
Compare this package's specification version with a desired version. |
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boolean |
isSealed()
Returns true if this package is sealed. |
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boolean |
isSealed(URL url)
Returns true if this package is sealed with respect to the specified code source url. |
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String |
toString()
Returns the string representation of this Package. |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, notify, notifyAll, wait, wait, wait |
Method Detail |
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public String getName()
public String getSpecificationTitle()
public String getSpecificationVersion()
public String getSpecificationVendor()
public String getImplementationTitle()
public String getImplementationVersion()
public String getImplementationVendor()
public boolean isSealed()
public boolean isSealed(URL url)
url
- the code source url
public boolean isCompatibleWith(String desired) throws NumberFormatException
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.
desired
- the version string of the desired version.
NumberFormatException
- if the desired or current version
is not of the correct dotted form.public static Package getPackage(String name)
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.
name
- a package name, for example, java.lang.
public static Package[] getPackages()
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.
ClassLoader
instance. An zero length array is returned if none are known.public int hashCode()
hashCode
in class Object
Object.equals(java.lang.Object)
,
Hashtable
public String toString()
toString
in class Object
public <A extends Annotation> A getAnnotation(Class<A> annotationClass)
AnnotatedElement
getAnnotation
in interface AnnotatedElement
annotationClass
- the Class object corresponding to the
annotation type
NullPointerException
- if the given annotation class is nullpublic boolean isAnnotationPresent(Class<? extends Annotation> annotationClass)
AnnotatedElement
isAnnotationPresent
in interface AnnotatedElement
annotationClass
- the Class object corresponding to the
annotation type
NullPointerException
- if the given annotation class is nullpublic Annotation[] getAnnotations()
AnnotatedElement
getAnnotations
in interface AnnotatedElement
public Annotation[] getDeclaredAnnotations()
AnnotatedElement
getDeclaredAnnotations
in interface AnnotatedElement
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Java™ Platform Standard Ed. 6 |
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