Skip to content

Most visited

Recently visited

navigation

Package

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) 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.

See also:

Summary

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 ClassLoader instance.

static Package[] getPackages()

Get all the packages currently known for the caller's ClassLoader instance.

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

Public methods

getAnnotation

Added in API level 9
A getAnnotation (Class<A> annotationClass)

Parameters
annotationClass Class
Returns
A
Throws
NullPointerException

getAnnotations

Added in API level 1
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

getAnnotationsByType

Added in API level 24
A[] getAnnotationsByType (Class<A> annotationClass)

Parameters
annotationClass Class
Returns
A[]
Throws
NullPointerException

getDeclaredAnnotation

Added in API level 24
A getDeclaredAnnotation (Class<A> annotationClass)

Parameters
annotationClass Class
Returns
A
Throws
NullPointerException

getDeclaredAnnotations

Added in API level 1
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

getDeclaredAnnotationsByType

Added in API level 24
A[] getDeclaredAnnotationsByType (Class<A> annotationClass)

Parameters
annotationClass Class
Returns
A[]
Throws
NullPointerException

getImplementationTitle

Added in API level 1
String getImplementationTitle ()

Return the title of this package.

Returns
String the title of the implementation, null is returned if it is not known.

getImplementationVendor

Added in API level 1
String getImplementationVendor ()

Returns the name of the organization, vendor or company that provided this implementation.

Returns
String the vendor that implemented this package..

getImplementationVersion

Added in API level 1
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.

getName

Added in API level 1
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

getPackage

Added in API level 1
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.

getPackages

Added in API level 1
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.

getSpecificationTitle

Added in API level 1
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.

getSpecificationVendor

Added in API level 1
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.

getSpecificationVersion

Added in API level 1
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.

hashCode

Added in API level 1
int hashCode ()

Return the hash code computed from the package name.

Returns
int the hash code computed from the package name.

isCompatibleWith

Added in API level 1
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.

isSealed

Added in API level 1
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

isSealed

Added in API level 1
boolean isSealed ()

Returns true if this package is sealed.

Returns
boolean true if the package is sealed, false otherwise

toString

Added in API level 1
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.
This site uses cookies to store your preferences for site-specific language and display options.

Hooray!

This class requires API level or higher

This doc is hidden because your selected API level for the documentation is . You can change the documentation API level with the selector above the left navigation.

For more information about specifying the API level your app requires, read Supporting Different Platform Versions.