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Class java.lang.Package

java.lang.Object
    |
    +----java.lang.Package

public class Package

extends Object

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 make 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.

getAllPackages()

Get all the packages currently known for the callers classloader.

getImplementationTitle()

Return the title of this package.

getImplementationVendor()

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

getImplementationVersion()

Return the version of this implementation.

getName()

Return the name of this package.

getPackage(String)

Find a package by name in the callers classloader.

getSealBase()

If the package is sealed, then returns the base URL from which the package was loaded.

getSpecificationTitle()

Return the title of the specification that this package implements.

getSpecificationVendor()

Return the name of the organization, vendor, or company that provided the classes that implement this package.

getSpecificationVersion()

Returns the version number of the specification that this package implements.

hashCode()

Return the hashcode computed from the name.

isCompatibleWith(String)

Compare this package's specification version with a desired version.

isSealed()

Returns true if the package is sealed.

toString()

Returns the string representation of this Package.

public String getName()

Return the name of this package.

Returns:

The name of this package using the Java language dot notation for the package. i.e java.lang

public String getSpecificationTitle()

Return the title of the specification that this package implements.

Returns:

the specification title.

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.

Returns:

the specification version..

public String getSpecificationVendor()

Return the name of the organization, vendor, or company that provided the classes that implement this package.

Returns:

the specification vendor.

public String getImplementationTitle()

Return the title of this package.

Returns:

the title of the implementation.

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.

public String getImplementationVendor()

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

Returns:

the vendor that implemented this package..

public boolean isSealed()

Returns true if the package is sealed. getSealBase() will return the base URL for sealing. Any classes loaded from the package must originate from the same base URL.

Returns:

true if the package is sealed, false otherwise

public URL getSealBase()

If the package is sealed, then returns the base URL from which the package was loaded. If the URL returned does not end with a '/' then it refers to a JAR file.

Returns:

the base URL that this package was loaded from, or null if the package was not sealed.

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 desired or current version is not of the correct dotted form.

public static Package getPackage(String name)

Find a package by name in the callers classloader. The callers classloader is used to find the package instance corresponding to the named class. If the callers classloader is null then the set of packages loaded by the system classloader is searched to find the named package.

Packages have attributes for versions and specifications only if the information the class loader created the package instance with the appropriate attributes. Typically those attributes are defined in the manifests that accompany the classes.

Parameters:

packageName - a package name, for example, java.lang.

Returns:

the package of the requested name. It may be null if no package information is available from the archive or codebase.

public static Package[] getAllPackages()

Get all the packages currently known for the callers classloader. Those packages correspond to classes loaded via or accessible by name to that classloader. If the callers classloader is null only the packages corresponding to system classes will be returned.

Returns:

an array of packages. An zero length array is returned if none are known.

See Also:

ClassLoader

public int hashCode()

Return the hashcode computed from the name.

Overrides:

hashCode in class Object

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:

the string representation of the package.

Overrides:

toString in class Object

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