@ SuppressWarnings ( "unchecked" ) protected void reduce ( KEYIN key , Iterable < VALUEIN > values , Context context ) throws IOException , InterruptedException { for ( VALUEIN value : values ) { context . write ( ( KEYOUT ) key , ( VALUEOUT ) value ) ; } }
This method is called once for each key . Most applications will define their reduce class by overriding this method . The default implementation is an identity function .