LookupCSV.java

Below is the syntax highlighted version of LookupCSV.java from §3.5 Searching Applications.

/******************************************************************************
 *  Compilation:  javac LookupCSV.java
 *  Execution:    java LookupCSV file.csv keyField valField
 *  Dependencies: ST.java In.java StdIn.java StdOut.java
 *  Data files:   https://algs4.cs.princeton.edu/35applications/DJIA.csv
 *                https://algs4.cs.princeton.edu/35applications/UPC.csv
 *                https://algs4.cs.princeton.edu/35applications/amino.csv
 *                https://algs4.cs.princeton.edu/35applications/elements.csv
 *                https://algs4.cs.princeton.edu/35applications/ip.csv
 *                https://algs4.cs.princeton.edu/35applications/morse.csv
 *
 *  Reads in a set of key-value pairs from a two-column CSV file
 *  specified on the command line; then, reads in keys from standard
 *  input and prints out corresponding values.
 *
 *  % java LookupCSV amino.csv 0 3     % java LookupCSV ip.csv 0 1
 *  TTA                                www.google.com
 *  Leucine                            216.239.41.99
 *  ABC
 *  Not found                          % java LookupCSV ip.csv 1 0
 *  TCT                                216.239.41.99
 *  Serine                             www.google.com
 *
 *  % java LookupCSV amino.csv 3 0     % java LookupCSV DJIA.csv 0 1
 *  Glycine                            29-Oct-29
 *  GGG                                252.38
 *                                     20-Oct-87
 *                                     1738.74
 *
 *
 ******************************************************************************/

/**
 *  The {@code LookupCSV} class provides a data-driven client for reading in a
 *  key-value pairs from a file; then, printing the values corresponding to the
 *  keys found on standard input. Both keys and values are strings.
 *  The fields to serve as the key and value are taken as command-line arguments.
 *  <p>
 *  For additional documentation, see <a href="https://algs4.cs.princeton.edu/35applications">Section 3.5</a> of
 *  <i>Algorithms, 4th Edition</i> by Robert Sedgewick and Kevin Wayne.
 *
 *  @author Robert Sedgewick
 *  @author Kevin Wayne
 */
public class LookupCSV {

    // Do not instantiate.
    private LookupCSV() { }

    public static void main(String[] args) {
        int keyField = Integer.parseInt(args[1]);
        int valField = Integer.parseInt(args[2]);

        // symbol table
        ST<String, String> st = new ST<String, String>();

        // read in the data from csv file
        In in = new In(args[0]);
        while (in.hasNextLine()) {
            String line = in.readLine();
            String[] tokens = line.split(",");
            String key = tokens[keyField];
            String val = tokens[valField];
            st.put(key, val);
        }

        while (!StdIn.isEmpty()) {
            String s = StdIn.readString();
            if (st.contains(s)) StdOut.println(st.get(s));
            else                StdOut.println("Not found");
        }
    }
}