Class: java.lang.Package
- public class Package
- implements AnnotatedElement
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 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) returns
true, 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.
Methods
-
getAnnotationtop
public <A extends Annotation> A getAnnotation(Class<A> annotationClass)Returns this element's annotation for the specified type if such an annotation is present, else null.- Specified by:
- getAnnotation from AnnotatedElement
-
getAnnotationstop
public 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.- Specified by:
- getAnnotations from AnnotatedElement
-
getDeclaredAnnotationstop
public 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.- Specified by:
- getDeclaredAnnotations from AnnotatedElement
-
getImplementationTitletop
public String getImplementationTitle()Return the title of this package. -
getImplementationVendortop
public String getImplementationVendor()Returns the name of the organization, vendor or company that provided this implementation. -
getImplementationVersiontop
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. -
getNametop
public String getName()Return the name of this package. -
getPackagetop
Find a package by name in the callersClassLoaderinstance. The callersClassLoaderinstance is used to find the package instance corresponding to the named class. If the callersClassLoaderinstance is null then the set of packages loaded by the systemClassLoaderinstance 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.
-
getPackagestop
public static Package[] getPackages()Get all the packages currently known for the caller'sClassLoaderinstance. Those packages correspond to classes loaded via or accessible by name to thatClassLoaderinstance. If the caller'sClassLoaderinstance is the bootstrapClassLoaderinstance, which may be represented bynullin some implementations, only packages corresponding to classes loaded by the bootstrapClassLoaderinstance will be returned. -
getSpecificationTitletop
public String getSpecificationTitle()Return the title of the specification that this package implements. -
getSpecificationVendortop
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. -
getSpecificationVersiontop
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. -
hashCodetop
public int hashCode()Return the hash code computed from the package name. -
isAnnotationPresenttop
public boolean isAnnotationPresent(Class<? extends Annotation> annotationClass)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.- Specified by:
- isAnnotationPresent from AnnotatedElement
-
isCompatibleWithtop
public boolean isCompatibleWith(String desired) throws NumberFormatExceptionCompare 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.
-
isSealedtop
public boolean isSealed()Returns true if this package is sealed. -
isSealedtop
public boolean isSealed(URL url)Returns true if this package is sealed with respect to the specified code source url. -
toStringtop
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.