hadoop - How to implement WritableComparable interface? -

i need use method setgroupingcomparatorclass in job , takes argument of type writablecomparable.

i unable implement writablecomparable class.

please me solve this. regards, bidyut

    setgroupingcomparatorclass(class<? extends rawcomparator> cls) 

define comparator controls keys grouped single call reducer.reduce(object, iterable, org.apache.hadoop.mapreduce.reducer.context)

    job.setgroupingcomparatorclass(customkey.groupcomparator.class); 

in customkey class can write static method.

add below code in custom key class.

public class customkey implements writablecomparable<indexerkey> {      public static class groupcomparator extends writablecomparator             implements serializable {         private static final long serialversionuid = -3385728040072507941l;          public groupcomparator() {              super(customkey .class, true);          }          @suppresswarnings("rawtypes")         public int compare(writablecomparable a, writablecomparable b) {              customkey w1 = (customkey ) a;              customkey w2 = (customkey ) b;              return w1.comparegroup(w2);         }      } } 

hope you.