Added in API level 1

Summary: Protected Ctors | Methods | Protected Methods | Inherited Methods | [Expand All]

ClassLoader

public abstract class ClassLoader
extends Object

java.lang.Object
↳	java.lang.ClassLoader

Known Direct Subclasses

BaseDexClassLoader, SecureClassLoader

Known Indirect Subclasses

DexClassLoader, PathClassLoader, URLClassLoader

Loads classes and resources from a repository. One or more class loaders are installed at runtime. These are consulted whenever the runtime system needs a specific class that is not yet available in-memory. Typically, class loaders are grouped into a tree where child class loaders delegate all requests to parent class loaders. Only if the parent class loader cannot satisfy the request, the child class loader itself tries to handle it.

ClassLoader is an abstract class that implements the common infrastructure required by all class loaders. Android provides several concrete implementations of the class, with PathClassLoader being the one typically used. Other applications may implement subclasses of ClassLoader to provide special ways for loading classes.

See also:

Class

Summary

Protected constructors
`ClassLoader()` Constructs a new instance of this class with the system class loader as its parent.
`ClassLoader(ClassLoader parentLoader)` Constructs a new instance of this class with the specified class loader as its parent.

Public methods
`void`	`clearAssertionStatus()` Sets the default assertion status for this class loader to `false` and removes any package default and class assertion status settings.
`final ClassLoader`	`getParent()` Returns this class loader's parent.
`URL`	`getResource(String resName)` Returns the URL of the resource with the specified name.
`InputStream`	`getResourceAsStream(String resName)` Returns a stream for the resource with the specified name.
`Enumeration<URL>`	`getResources(String resName)` Returns an enumeration of URLs for the resource with the specified name.
`static ClassLoader`	`getSystemClassLoader()` Returns the system class loader.
`static URL`	`getSystemResource(String resName)` Finds the URL of the resource with the specified name.
`static InputStream`	`getSystemResourceAsStream(String resName)` Returns a stream for the resource with the specified name.
`static Enumeration<URL>`	`getSystemResources(String resName)` Returns an enumeration of URLs for the resource with the specified name.
`Class<?>`	`loadClass(String className)` Loads the class with the specified name.
`void`	`setClassAssertionStatus(String cname, boolean enable)` Sets the assertion status of the class with the specified name.
`void`	`setDefaultAssertionStatus(boolean enable)` Sets the default assertion status for this class loader.
`void`	`setPackageAssertionStatus(String pname, boolean enable)` Sets the assertion status of the package with the specified name.

Protected methods
`final Class<?>`	`defineClass(String name, ByteBuffer b, ProtectionDomain protectionDomain)` Defines a new class with the specified name, byte code from the byte buffer and the optional protection domain.
`final Class<?>`	`defineClass(String className, byte[] classRep, int offset, int length, ProtectionDomain protectionDomain)` Constructs a new class from an array of bytes containing a class definition in class file format and assigns the specified protection domain to the new class.
`final Class<?>`	`defineClass(String className, byte[] classRep, int offset, int length)` Constructs a new class from an array of bytes containing a class definition in class file format.
`final Class<?>`	`defineClass(byte[] classRep, int offset, int length)` This method was deprecated in API level 1. Use `defineClass(String, byte[], int, int)`
`Package`	`definePackage(String name, String specTitle, String specVersion, String specVendor, String implTitle, String implVersion, String implVendor, URL sealBase)` Defines and returns a new `Package` using the specified information.
`Class<?>`	`findClass(String className)` Overridden by subclasses, throws a `ClassNotFoundException` by default.
`String`	`findLibrary(String libName)` Returns the absolute path of the native library with the specified name, or `null`.
`final Class<?>`	`findLoadedClass(String className)` Returns the class with the specified name if it has already been loaded by the VM or `null` if it has not yet been loaded.
`URL`	`findResource(String resName)` Finds the URL of the resource with the specified name.
`Enumeration<URL>`	`findResources(String resName)` Finds an enumeration of URLs for the resource with the specified name.
`final Class<?>`	`findSystemClass(String className)` Finds the class with the specified name, loading it using the system class loader if necessary.
`Package`	`getPackage(String name)` Returns the package with the specified name.
`Package[]`	`getPackages()` Returns all the packages known to this class loader.
`Class<?>`	`loadClass(String className, boolean resolve)` Loads the class with the specified name, optionally linking it after loading.
`final void`	`resolveClass(Class<?> clazz)` Forces a class to be linked (initialized).
`final void`	`setSigners(Class<?> c, Object[] signers)` Sets the signers of the specified class.

Inherited methods

From class


  
    java.lang.Object

`Object`	`clone()` Creates and returns a copy of this `Object`.
`boolean`	`equals(Object o)` Compares this instance with the specified object and indicates if they are equal.
`void`	`finalize()` Invoked when the garbage collector has detected that this instance is no longer reachable.
`final Class<?>`	`getClass()` Returns the unique instance of `Class` that represents this object's class.
`int`	`hashCode()` Returns an integer hash code for this object.
`final void`	`notify()` Causes a thread which is waiting on this object's monitor (by means of calling one of the `wait()` methods) to be woken up.
`final void`	`notifyAll()` Causes all threads which are waiting on this object's monitor (by means of calling one of the `wait()` methods) to be woken up.
`String`	`toString()` Returns a string containing a concise, human-readable description of this object.
`final void`	`wait()` Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object.
`final void`	`wait(long millis, int nanos)` Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object or until the specified timeout expires.
`final void`	`wait(long millis)` Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object or until the specified timeout expires.

Protected constructors

ClassLoader

Added in API level 1

ClassLoader ()

Constructs a new instance of this class with the system class loader as its parent.

ClassLoader

Added in API level 1

ClassLoader (ClassLoader parentLoader)

Constructs a new instance of this class with the specified class loader as its parent.

Parameters
`parentLoader`	`ClassLoader`: The `ClassLoader` to use as the new class loader's parent.

Public methods

clearAssertionStatus

Added in API level 1

void clearAssertionStatus ()

Sets the default assertion status for this class loader to false and removes any package default and class assertion status settings.

Note: This method does nothing in the Android reference implementation.

getParent

Added in API level 1

ClassLoader getParent ()

Returns this class loader's parent.

Returns
`ClassLoader`	this class loader's parent or `null`.

getResource

Added in API level 1

URL getResource (String resName)

Returns the URL of the resource with the specified name. This implementation first tries to use the parent class loader to find the resource; if this fails then findResource(String) is called to find the requested resource.

Parameters
`resName`	`String`: the name of the resource to find.

Returns
`URL`	the `URL` object for the requested resource or `null` if the resource can not be found

See also:

getResource(String)

getResourceAsStream

Added in API level 1

InputStream getResourceAsStream (String resName)

Returns a stream for the resource with the specified name. See getResource(String) for a description of the lookup algorithm used to find the resource.

Parameters
`resName`	`String`: the name of the resource to find.

Returns
`InputStream`	a stream for the resource or `null` if the resource can not be found

See also:

getResourceAsStream(String)

getResources

Added in API level 1

Enumeration<URL> getResources (String resName)

Returns an enumeration of URLs for the resource with the specified name. This implementation first uses this class loader's parent to find the resource, then it calls findResources(String) to get additional URLs. The returned enumeration contains the URL objects of both find operations.

Parameters
`resName`	`String`: the name of the resource to find.

Returns
`Enumeration<URL>`	an enumeration of `URL` objects for the requested resource.

Throws
`IOException`	if an I/O error occurs.

getSystemClassLoader

Added in API level 1

ClassLoader getSystemClassLoader ()

Returns the system class loader. This is the parent for new ClassLoader instances and is typically the class loader used to start the application.

Returns
`ClassLoader`

getSystemResource

Added in API level 1

URL getSystemResource (String resName)

Finds the URL of the resource with the specified name. The system class loader's resource lookup algorithm is used to find the resource.

Parameters
`resName`	`String`: the name of the resource to find.

Returns
`URL`	the `URL` object for the requested resource or `null` if the resource can not be found.

See also:

getResource(String)

getSystemResourceAsStream

Added in API level 1

InputStream getSystemResourceAsStream (String resName)

Returns a stream for the resource with the specified name. The system class loader's resource lookup algorithm is used to find the resource. Basically, the contents of the java.class.path are searched in order, looking for a path which matches the specified resource.

Parameters
`resName`	`String`: the name of the resource to find.

Returns
`InputStream`	a stream for the resource or `null`.

See also:

getResourceAsStream(String)

getSystemResources

Added in API level 1

Enumeration<URL> getSystemResources (String resName)

Returns an enumeration of URLs for the resource with the specified name. The system class loader's resource lookup algorithm is used to find the resource.

Parameters
`resName`	`String`: the name of the resource to find.

Returns
`Enumeration<URL>`	an enumeration of `URL` objects containing the requested resources.

Throws
`IOException`	if an I/O error occurs.

loadClass

Added in API level 1

Class<?> loadClass (String className)

Loads the class with the specified name. Invoking this method is equivalent to calling loadClass(className, false).

Note: In the Android reference implementation, the second parameter of loadClass(String, boolean) is ignored anyway.

Parameters
`className`	`String`: the name of the class to look for.

Returns
`Class<?>`	the `Class` object.

Throws
`ClassNotFoundException`	if the class can not be found.

setClassAssertionStatus

Added in API level 1

void setClassAssertionStatus (String cname, 
                boolean enable)

Sets the assertion status of the class with the specified name.

Note: This method does nothing in the Android reference implementation.

Parameters
`cname`	`String`: the name of the class for which to set the assertion status.
`enable`	`boolean`: the new assertion status.

setDefaultAssertionStatus

Added in API level 1

void setDefaultAssertionStatus (boolean enable)

Sets the default assertion status for this class loader.

Note: This method does nothing in the Android reference implementation.

Parameters
`enable`	`boolean`: the new assertion status.

setPackageAssertionStatus

Added in API level 1

void setPackageAssertionStatus (String pname, 
                boolean enable)

Sets the assertion status of the package with the specified name.

Note: This method does nothing in the Android reference implementation.

Parameters
`pname`	`String`: the name of the package for which to set the assertion status.
`enable`	`boolean`: the new assertion status.

Protected methods

defineClass

Added in API level 1

Class<?> defineClass (String name, 
                ByteBuffer b, 
                ProtectionDomain protectionDomain)

Defines a new class with the specified name, byte code from the byte buffer and the optional protection domain. If the provided protection domain is null then a default protection domain is assigned to the class.

Parameters
`name`	`String`: the expected name of the new class, may be `null` if not known.
`b`	`ByteBuffer`: the byte buffer containing the byte code of the new class.
`protectionDomain`	`ProtectionDomain`: the protection domain to assign to the loaded class, may be `null`.

Returns
`Class<?>`	the `Class` object created from the data in `b`.

Throws
`ClassFormatError`	if `b` does not contain a valid class.
`NoClassDefFoundError`	if `className` is not equal to the name of the class contained in `b`.

defineClass

Added in API level 1

Class<?> defineClass (String className, 
                byte[] classRep, 
                int offset, 
                int length, 
                ProtectionDomain protectionDomain)

Constructs a new class from an array of bytes containing a class definition in class file format and assigns the specified protection domain to the new class. If the provided protection domain is null then a default protection domain is assigned to the class.

Parameters
`className`	`String`: the expected name of the new class, may be `null` if not known.
`classRep`	`byte`: the memory image of a class file.
`offset`	`int`: the offset into `classRep`.
`length`	`int`: the length of the class file.
`protectionDomain`	`ProtectionDomain`: the protection domain to assign to the loaded class, may be `null`.

Returns
`Class<?>`	the `Class` object created from the specified subset of data in `classRep`.

Throws
`ClassFormatError`	if `classRep` does not contain a valid class.
`IndexOutOfBoundsException`	if `offset < 0`, `length < 0` or if `offset + length` is greater than the length of `classRep`.
`NoClassDefFoundError`	if `className` is not equal to the name of the class contained in `classRep`.

defineClass

Added in API level 1

Class<?> defineClass (String className, 
                byte[] classRep, 
                int offset, 
                int length)

Constructs a new class from an array of bytes containing a class definition in class file format.

Parameters
`className`	`String`: the expected name of the new class, may be `null` if not known.
`classRep`	`byte`: the memory image of a class file.
`offset`	`int`: the offset into `classRep`.
`length`	`int`: the length of the class file.

Returns
`Class<?>`	the `Class` object created from the specified subset of data in `classRep`.

Throws
`ClassFormatError`	if `classRep` does not contain a valid class.
`IndexOutOfBoundsException`	if `offset < 0`, `length < 0` or if `offset + length` is greater than the length of `classRep`.

defineClass

Added in API level 1

Class<?> defineClass (byte[] classRep, 
                int offset, 
                int length)

This method was deprecated in API level 1.
Use defineClass(String, byte[], int, int)

Constructs a new class from an array of bytes containing a class definition in class file format.

Parameters
`classRep`	`byte`: the memory image of a class file.
`offset`	`int`: the offset into `classRep`.
`length`	`int`: the length of the class file.

Returns
`Class<?>`	the `Class` object created from the specified subset of data in `classRep`.

Throws
`ClassFormatError`	if `classRep` does not contain a valid class.
`IndexOutOfBoundsException`	if `offset < 0`, `length < 0` or if `offset + length` is greater than the length of `classRep`.

definePackage

Added in API level 1

Package definePackage (String name, 
                String specTitle, 
                String specVersion, 
                String specVendor, 
                String implTitle, 
                String implVersion, 
                String implVendor, 
                URL sealBase)

Defines and returns a new Package using the specified information. If sealBase is null, the package is left unsealed. Otherwise, the package is sealed using this URL.

Parameters
`name`	`String`: the name of the package.
`specTitle`	`String`: the title of the specification.
`specVersion`	`String`: the version of the specification.
`specVendor`	`String`: the vendor of the specification.
`implTitle`	`String`: the implementation title.
`implVersion`	`String`: the implementation version.
`implVendor`	`String`: the specification vendor.
`sealBase`	`URL`: the URL used to seal this package or `null` to leave the package unsealed.

Returns
`Package`	the `Package` object that has been created.

Throws
`IllegalArgumentException`	if a package with the specified name already exists.

findClass

Added in API level 1

Class<?> findClass (String className)

Overridden by subclasses, throws a ClassNotFoundException by default. This method is called by loadClass after the parent ClassLoader has failed to find a loaded class of the same name.

Parameters
`className`	`String`: the name of the class to look for.

Returns
`Class<?>`	the `Class` object that is found.

Throws
`ClassNotFoundException`	if the class cannot be found.

findLibrary

Added in API level 1

String findLibrary (String libName)

Returns the absolute path of the native library with the specified name, or null. If this method returns null then the virtual machine searches the directories specified by the system property "java.library.path".

This implementation always returns null.

Parameters
`libName`	`String`: the name of the library to find.

Returns
`String`	the absolute path of the library.

findLoadedClass

Added in API level 1

Class<?> findLoadedClass (String className)

Returns the class with the specified name if it has already been loaded by the VM or null if it has not yet been loaded.

Parameters
`className`	`String`: the name of the class to look for.

Returns
`Class<?>`	the `Class` object or `null` if the requested class has not been loaded.

findResource

Added in API level 1

URL findResource (String resName)

Finds the URL of the resource with the specified name. This implementation just returns null; it should be overridden in subclasses.

Parameters
`resName`	`String`: the name of the resource to find.

Returns
`URL`	the `URL` object for the requested resource.

findResources

Added in API level 1

Enumeration<URL> findResources (String resName)

Finds an enumeration of URLs for the resource with the specified name. This implementation just returns an empty Enumeration; it should be overridden in subclasses.

Parameters
`resName`	`String`: the name of the resource to find.

Returns
`Enumeration<URL>`	an enumeration of `URL` objects for the requested resource.

Throws
`IOException`	if an I/O error occurs.

findSystemClass

Added in API level 1

Class<?> findSystemClass (String className)

Finds the class with the specified name, loading it using the system class loader if necessary.

Parameters
`className`	`String`: the name of the class to look for.

Returns
`Class<?>`	the `Class` object with the requested `className`.

Throws
`ClassNotFoundException`	if the class can not be found.

getPackage

Added in API level 1

Package getPackage (String name)

Returns the package with the specified name. Package information is searched in this class loader.

Parameters
`name`	`String`: the name of the package to find.

Returns
`Package`	the package with the requested name; `null` if the package can not be found.

getPackages

Added in API level 1

Package[] getPackages ()

Returns all the packages known to this class loader.

Returns
`Package[]`	an array with all packages known to this class loader.

loadClass

Added in API level 1

Class<?> loadClass (String className, 
                boolean resolve)

Loads the class with the specified name, optionally linking it after loading. The following steps are performed:

Call findLoadedClass(String) to determine if the requested class has already been loaded.
If the class has not yet been loaded: Invoke this method on the parent class loader.
If the class has still not been loaded: Call findClass(String) to find the class.

Note: In the Android reference implementation, the resolve parameter is ignored; classes are never linked.

Parameters
`className`	`String`: the name of the class to look for.
`resolve`	`boolean`: Indicates if the class should be resolved after loading. This parameter is ignored on the Android reference implementation; classes are not resolved.

Returns
`Class<?>`	the `Class` object.

Throws
`ClassNotFoundException`	if the class can not be found.

resolveClass

Added in API level 1

void resolveClass (Class<?> clazz)

Forces a class to be linked (initialized). If the class has already been linked this operation has no effect.

Note: In the Android reference implementation, this method has no effect.

Parameters
`clazz`	`Class`: the class to link.

setSigners

Added in API level 1

void setSigners (Class<?> c, 
                Object[] signers)

Sets the signers of the specified class. This implementation does nothing.

Parameters
`c`	`Class`: the `Class` object for which to set the signers.
`signers`	`Object`: the signers for `c`.

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Apr	MAY	Jun
	30
2015	2016	2017

ClassLoader

Summary

Protected constructors

Public methods

Protected methods

Inherited methods

Protected constructors

ClassLoader

ClassLoader

Public methods

clearAssertionStatus

getParent

getResource

getResourceAsStream

getResources

getSystemClassLoader

getSystemResource

getSystemResourceAsStream

getSystemResources

loadClass

setClassAssertionStatus

setDefaultAssertionStatus

setPackageAssertionStatus

Protected methods

defineClass

defineClass

defineClass

defineClass

definePackage

findClass

findLibrary

findLoadedClass

findResource

findResources

findSystemClass

getPackage

getPackages

loadClass

resolveClass

setSigners

Annotations

Interfaces

Classes

Enums

Exceptions

Errors