- java.lang.Object
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- java.lang.Package
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- All Implemented Interfaces:
AnnotatedElement
public class Package extends Object implements AnnotatedElement
Represents metadata about a run-time package associated with a class loader. Metadata includes annotations, versioning, and sealing.Annotations for the run-time package are read from
package-info.classat 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
Packageis defined. An application can ask if thePackageis compatible with a particular specification version by using thePackage.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
Packagemay be explicitly defined with theClassLoader.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 aPackageis not explicitly defined for a run-time package when a class in that run-time package is defined, then aPackageis automatically defined by the class's defining class loader, as follows.A
Packageautomatically 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.classas specified above.
A
Packageautomatically 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.classas specified above.
A
Packagecan be obtained with thePackage.getPackage(String)andClassLoader.getDefinedPackage(String)methods. EveryPackagedefined by a class loader can be obtained with thePackage.getPackages()andClassLoader.getDefinedPackages()methods.- Implementation Note:
- The builtin class loaders
do not explicitly define
Packageobjects for packages in named modules. Instead those packages are automatically defined and have no specification and implementation versioning information. - Since:
- 1.2
- See Also:
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The JAR File Specification: Package Sealing,
ClassLoader.definePackage(String, String, String, String, String, String, String, URL) - See The Java™ Virtual Machine Specification:
- 5.3 Run-time package
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Deprecated Methods 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.StringgetImplementationTitle()Return the title of this package.StringgetImplementationVendor()Returns the vendor that implemented this package,nullis returned if it is not known.StringgetImplementationVersion()Return the version of this implementation.StringgetName()Return the name of this package.static PackagegetPackage(String name)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 ofgetPackageto return aPackagefrom a parent loader, then the properties exposed by thePackagemay not be as expected in the rest of the program.static Package[]getPackages()Returns all of thePackages defined by the caller's class loader and its ancestors.StringgetSpecificationTitle()Return the title of the specification that this package implements.StringgetSpecificationVendor()Return the name of the organization, vendor, or company that owns and maintains the specification of the classes that implement this package.StringgetSpecificationVersion()Returns the version number of the specification that this package implements.inthashCode()Return the hash code computed from the package name.booleanisAnnotationPresent(Class<? extends Annotation> annotationClass)Returns true if an annotation for the specified type is present on this element, else false.booleanisCompatibleWith(String desired)Compare this package's specification version with a desired version.booleanisSealed()Returns true if this package is sealed.booleanisSealed(URL url)Returns true if this package is sealed with respect to the specified code sourceurl.StringtoString()Returns the string representation of this Package.
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Method Detail
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getName
public String 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
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getSpecificationTitle
public String getSpecificationTitle()
Return the title of the specification that this package implements.- Returns:
- the specification title,
nullis returned if it is not known.
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getSpecificationVersion
public String 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,
nullis returned if it is not known.
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getSpecificationVendor
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:
- the specification vendor,
nullis returned if it is not known.
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getImplementationTitle
public String getImplementationTitle()
Return the title of this package.- Returns:
- the title of the implementation,
nullis returned if it is not known.
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getImplementationVersion
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:
- the version of the implementation,
nullis returned if it is not known.
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getImplementationVendor
public String getImplementationVendor()
Returns the vendor that implemented this package,nullis returned if it is not known.- Returns:
- the vendor that implemented this package,
nullis returned if it is not known.
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isSealed
public boolean isSealed()
Returns true if this package is sealed.- Returns:
- true if the package is sealed, false otherwise
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isSealed
public boolean isSealed(URL url)
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
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isCompatibleWith
public boolean isCompatibleWith(String desired) throws NumberFormatException
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.
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getPackage
@Deprecated(since="9") public static Package getPackage(String name)
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 ofgetPackageto return aPackagefrom a parent loader, then the properties exposed by thePackagemay not be as expected in the rest of the program. For example, thePackagewill only expose annotations from thepackage-info.classfile defined by the parent loader, even if annotations exist in apackage-info.classfile defined by a child loader. A more robust approach is to use theClassLoader.getDefinedPackage(java.lang.String)method which returns aPackagefor 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
Packageof the given name, thePackageis returned. Otherwise, the ancestors of the caller's class loader are searched recursively (parent by parent) for aPackageof the given name.Calling this method is equivalent to calling
ClassLoader.getPackage(java.lang.String)on aClassLoaderinstance which is the caller's class loader.- Parameters:
name- A package name, such as "java.lang".- Returns:
- The
Packageof the given name defined by the caller's class loader or its ancestors, ornullif not found. - Throws:
NullPointerException- ifnameisnull.- See Also:
ClassLoader.getDefinedPackage(java.lang.String)
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getPackages
public static Package[] getPackages()
Returns all of thePackages defined by the caller's class loader and its ancestors. The returned array may contain more than onePackageobject 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 aClassLoaderinstance which is the caller's class loader.- Returns:
- The array of
Packageobjects defined by this class loader and its ancestors - See Also:
ClassLoader.getDefinedPackages()
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hashCode
public int hashCode()
Return the hash code computed from the package name.- Overrides:
hashCodein classObject- Returns:
- the hash code computed from the package name.
- See Also:
Object.equals(java.lang.Object),System.identityHashCode(java.lang.Object)
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toString
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.
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getAnnotation
public <A extends Annotation> A getAnnotation(Class<A> annotationClass)
Description copied from interface:AnnotatedElementReturns this element's annotation for the specified type if such an annotation is present, else null.- Specified by:
getAnnotationin 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
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isAnnotationPresent
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) != nullThe body of the default method is specified to be the code above.
- Specified by:
isAnnotationPresentin 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
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getAnnotationsByType
public <A extends Annotation> A[] getAnnotationsByType(Class<A> annotationClass)
Description copied from interface:AnnotatedElementReturns 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.- Specified by:
getAnnotationsByTypein 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
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getAnnotations
public Annotation[] getAnnotations()
Description copied from interface:AnnotatedElementReturns 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.- Specified by:
getAnnotationsin interfaceAnnotatedElement- Returns:
- annotations present on this element
- Since:
- 1.5
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getDeclaredAnnotation
public <A extends Annotation> A getDeclaredAnnotation(Class<A> annotationClass)
Description copied from interface:AnnotatedElementReturns 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.)- Specified by:
getDeclaredAnnotationin 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
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getDeclaredAnnotationsByType
public <A extends Annotation> A[] getDeclaredAnnotationsByType(Class<A> annotationClass)
Description copied from interface:AnnotatedElementReturns 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:
getDeclaredAnnotationsByTypein 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
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getDeclaredAnnotations
public Annotation[] getDeclaredAnnotations()
Description copied from interface:AnnotatedElementReturns 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.- Specified by:
getDeclaredAnnotationsin interfaceAnnotatedElement- Returns:
- annotations directly present on this element
- Since:
- 1.5
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