This document contains code for implementing an inverted index using Apache Hadoop MapReduce. The code includes a main class that sets up the job, a LineIndexMapper class containing the map method to tokenize text and output (word, document) pairs, and a LineIndexReducer class containing the reduce method to aggregate values for each word key into a comma-separated string. The code implements the basic MapReduce pattern of mapping input data to intermediate key-value pairs, shuffling, and reducing to output the final index.