java - how to write hadoop map reduce programs in scala -

i writing map reduce application scala. till map function works fine. while writing reducer facing problem.

override def reduce(key: text, values: java.lang.iterable[text],                      context: reducercontext) { } 

the reducercontext defined such refers context inner class, fine here.

the issue iterable (java) component.i not able iterate through it. understand first have convert scala iterable , iterate on it, did still didnt get result.

i have tried both scala.collection.javaconverters._ , javaconversions._ here few scanarios didnt work out

val jit: java.util.iterator[text]= values.iterator() val abc = javaconversions.asscalaiterator(jit) /// val abc=jit.asscala println("size "+ abc.size)// displays proper size for(temp <- abc){ ///it dosent come inside loop } 

similarly have tried converting iterator list/array in vain. once convert list/arrray(tolist/tiarray) size of resulting list/array becomes 0. no matter m not able iterate thorough

i appreciate on this.

thanks

you can import javaconversions convert iterable automatically.

import scala.collection.javaconversions._ 

if still have problem, can paste codes?

the tricky thing of values receive in reduce can traversed once. abc.size traverse values. after that, values invalid.

so correct code should be

// don't use values for(value <- values) {     //     string v = value.tostring     // don't save value, reused. content of value changed reference same. } // don't use values 

just mentioned in comment, type of value text. when traverse values, content of value changed, reference same. don't try save value in collection, or collection of items same.