Returns the system-wide default selector provider for this invocation of the Java virtual machine.
The first invocation of this method locates the default provider object as follows:
If the system property java.nio.channels.spi.SelectorProvider is defined then it is taken to be the fully-qualified name of a concrete provider class. The class is loaded and instantiated; if this process fails then an unspecified error is thrown.
If a provider class has been installed in a jar file that is visible to the system class loader, and that jar file contains a provider-configuration file named java.nio.channels.spi.SelectorProvider in the resource directory META-INF/services, then the first class name specified in that file is taken. The class is loaded and instantiated; if this process fails then an unspecified error is thrown.
Finally, if no provider has been specified by any of the above means then the system-default provider class is instantiated and the result is returned.
Subsequent invocations of this method return the provider that was returned by the first invocation.
Diagram: Selector