InvertedIndex.java

Below is the syntax highlighted version of InvertedIndex.java from §4.4 Symbol Tables.

/******************************************************************************
 *  Compilation:  javac InvertedIndex.java
 *  Execution:    java InvertedIndex list-of-filenames
 *  Dependencies: ST.java SET.java In.java StdIn.java
 *
 *  % java InvertedIndex *.java
 *  set
 *  ExceptionFilter.java InvertedIndex.java Lookup.java SET.java StdRandom.java
 *
 *  self-referential-search
 *  InvertedIndex.java
 *
 ******************************************************************************/

public class InvertedIndex {

    public static void main(String[] args) {

        // key = word, value = set of filenames containing that word
        ST<String, SET<String>> st = new ST<String, SET<String>>();

        // create inverted index of all files
        for (String filename : args) {
            // StdOut.println(filename);
            In in = new In(filename);
            while (!in.isEmpty()) {
                String word = in.readString();
                if (!st.contains(word)) st.put(word, new SET<String>());
                SET<String> set = st.get(word);
                set.add(filename);
            }
        }

        // read queries from standard input, one per line
        while (!StdIn.isEmpty()) {
            String query = StdIn.readString();
            if (!st.contains(query)) StdOut.println("NOT FOUND");
            else {
                SET<String> set = st.get(query);
                for (String filename : set) {
                    StdOut.print(filename + " ");
                }
                StdOut.println();
            }
            StdOut.println();
        }

    }

}