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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 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 "Dewey Decimal" 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 number must begin with a number.
The package title, package, and vendor strings identify an implementation and are made available conveniently to enable accurate reporting of the packages involved when a problem occurs. The version strings have no specified syntax and may only be compared for equality with desired version identifers. The contents are vendor specific.
Within each classloader 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.
Method Summary | |
static Package[] | getAllPackages()
|
String | getImplementationTitle()
|
String | getImplementationVendor()
|
String | getImplementationVersion()
|
String | getName()
|
static Package | getPackage(String name)
|
URL | getSealBase()
|
String | getSpecificationTitle()
|
String | getSpecificationVendor()
|
String | getSpecificationVersion()
|
int | hashCode()
|
boolean | isCompatibleWith(String desired)
|
boolean | isSealed()
|
String | toString()
|
Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Method Detail |
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 URL getSealBase()
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.
public static Package getPackage(String name)
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.
packageName
- a package name, for example, java.lang.
public static Package[] getAllPackages()
public int hashCode()
public String toString()
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