Custom Key in map reduce

You can create your custom key in your map reduce program.

Just implement WritableComparable interface.

Steps -

1. Create one class.
2. Extend it from WritableComparable interface.
1. Refernce  - https://hadoop.apache.org/docs/r2.6.1/api/org/apache/hadoop/io/WritableComparable.html
3. Override and implement compareTo method.
4. Override and implement equals method.
5. Override and implement hashCode method.
6. Override and implement readFields method.
7. Override and implement write method.

Study More - http://hadooptutorial.info/creating-custom-hadoop-writable-data-type/