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

This method is first invoked early in the runtime's startup sequence, at which point it creates the system class loader and sets it as the context class loader of the invoking Thread.

The default system class loader is an implementation-dependent instance of this class.

If the system property "java.system.class.loader" is defined when this method is first invoked then the value of that property is taken to be the name of a class that will be returned as the system class loader. The class is loaded using the default system class loader and must define a public constructor that takes a single parameter of type ClassLoader which is used as the delegation parent. An instance is then created using this constructor with the default system class loader as the parameter. The resulting class loader is defined to be the system class loader.

If a security manager is present, and the invoker's class loader is not null and the invoker's class loader is not the same as or an ancestor of the system class loader, then this method invokes the security manager's SecurityManager.checkPermission(java.security.Permission) method with a RuntimePermission.RuntimePermission(String) permission to verify access to the system class loader. If not, a SecurityException will be thrown.

Returns: The system ClassLoader for delegation, or null if none

Exceptions:

SecurityException     If a security manager exists and its checkPermission method doesn't allow access to the system class loader.

IllegalStateException     If invoked recursively during the construction of the class loader specified by the "java.system.class.loader" property.

Error     If the system property "java.system.class.loader" is defined but the named class could not be loaded, the provider class does not define the required constructor, or an exception is thrown by that constructor when it is invoked. The underlying cause of the error can be retrieved via the Throwable.getCause() method.

@revised 1.4

`SecurityException`		If a security manager exists and its `checkPermission` method doesn't allow access to the system class loader.
`IllegalStateException`		If invoked recursively during the construction of the class loader specified by the "`java.system.class.loader`" property.
`Error`		If the system property "`java.system.class.loader`" is defined but the named class could not be loaded, the provider class does not define the required constructor, or an exception is thrown by that constructor when it is invoked. The underlying cause of the error can be retrieved via the `Throwable.getCause()` method.