Added in API level 1

Summary: Methods | Inherited Methods

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 RefinedVersion_opt
RefinedVersion:
. Digits
. Digits RefinedVersion
Digits:
Digit
Digits
Digit:
any character for which Character#isDigit 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:

ClassLoader.definePackage(String, String, String, String, String, String, String, URL)

Summary

Public methods
`<A extends Annotation> A`	`getAnnotation(Class<A> annotationClass)`
`Annotation[]`	`getAnnotations()` Returns annotations that are present on this element.
`<A extends Annotation> A[]`	`getAnnotationsByType(Class<A> annotationClass)`
`<A extends Annotation> A`	`getDeclaredAnnotation(Class<A> annotationClass)`
`Annotation[]`	`getDeclaredAnnotations()` Returns 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`	`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(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

`Object`	`clone()` Creates and returns a copy of this object.
`boolean`	`equals(Object obj)` Indicates whether some other object is "equal to" this one.
`void`	`finalize()` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
`final Class<?>`	`getClass()` Returns the runtime class of this `Object`.
`int`	`hashCode()` Returns a hash code value for the object.
`final void`	`notify()` Wakes up a single thread that is waiting on this object's monitor.
`final void`	`notifyAll()` Wakes up all threads that are waiting on this object's monitor.
`String`	`toString()` Returns a string representation of the object.
`final void`	`wait(long timeoutMillis, int nanos)` Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
`final void`	`wait(long timeoutMillis)` Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
`final void`	`wait()` Causes the current thread to wait until it is awakened, typically by being notified or interrupted.

From interface


        
          java.lang.reflect.AnnotatedElement

`abstract <T extends Annotation> T`	`getAnnotation(Class<T> annotationClass)` Returns this element's annotation for the specified type if such an annotation is present, else null.
`abstract Annotation[]`	`getAnnotations()` Returns annotations that are present on this element.
`default <T extends Annotation> T[]`	`getAnnotationsByType(Class<T> annotationClass)` Returns annotations that are associated with this element.
`default <T extends Annotation> T`	`getDeclaredAnnotation(Class<T> annotationClass)` Returns this element's annotation for the specified type if such an annotation is directly present, else null.
`abstract Annotation[]`	`getDeclaredAnnotations()` Returns annotations that are directly present on this element.
`default <T extends Annotation> T[]`	`getDeclaredAnnotationsByType(Class<T> annotationClass)` Returns this element's annotation(s) for the specified type if such annotations are either directly present or indirectly present.
`default boolean`	`isAnnotationPresent(Class<? extends Annotation> annotationClass)` Returns true if an annotation for the specified type is present on this element, else false.

Public methods

getAnnotation

Added in API level 1

public A getAnnotation (Class<A> annotationClass)

Parameters
`annotationClass`	`Class`

Returns
`A`

Throws
`NullPointerException`

getAnnotations

Added in API level 1

public Annotation[] 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.

Returns
`Annotation[]`	annotations present on this element

getAnnotationsByType

Added in API level 24

public A[] getAnnotationsByType (Class<A> annotationClass)

Parameters
`annotationClass`	`Class`

Returns
`A[]`

Throws
`NullPointerException`

getDeclaredAnnotation

Added in API level 24

public A getDeclaredAnnotation (Class<A> annotationClass)

Parameters
`annotationClass`	`Class`

Returns
`A`

Throws
`NullPointerException`

getDeclaredAnnotations

Added in API level 1

public Annotation[] 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.

Returns
`Annotation[]`	annotations directly present on this element

getDeclaredAnnotationsByType

Added in API level 24

public A[] getDeclaredAnnotationsByType (Class<A> annotationClass)

Parameters
`annotationClass`	`Class`

Returns
`A[]`

Throws
`NullPointerException`

getImplementationTitle

Added in API level 1

public 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

public 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

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.

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

getName

Added in API level 1

public 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

public static 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

public static 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

public 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

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.

Returns
`String`	the specification vendor, null is returned if it is not known.

getSpecificationVersion

Added in API level 1

public 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

public int hashCode ()

Return the hash code computed from the package name.

Returns
`int`	the hash code computed from the package name.

isAnnotationPresent

Added in API level 1

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.

The truth value returned by this method is equivalent to: getAnnotation(annotationClass) != null

The body of the default method is specified to be the code above.

Parameters
`annotationClass`	`Class`: the Class object corresponding to the annotation type

Returns
`boolean`	true if an annotation for the specified annotation type is present on this element, else false

Throws
`NullPointerException`

isCompatibleWith

Added in API level 1

public 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

public 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

public 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

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.

Returns
`String`	the string representation of the package.