BlackFilter.java


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


/******************************************************************************
 *  Compilation:  javac BlackFilter.java
 *  Execution:    java BlackFilter blacklist.txt < input.txt
 *  Dependencies: SET In.java StdIn.java StdOut.java
 *  Data files:   https://algs4.cs.princeton.edu/35applications/tinyTale.txt
 *                https://algs4.cs.princeton.edu/35applications/list.txt
 *
 *  Read in a blacklist of words from a file. Then read in a list of
 *  words from standard input and print out all those words that
 *  are not in the first file.
 * 
 *  % more tinyTale.txt 
 *  it was the best of times it was the worst of times 
 *  it was the age of wisdom it was the age of foolishness 
 *  it was the epoch of belief it was the epoch of incredulity 
 *  it was the season of light it was the season of darkness 
 *  it was the spring of hope it was the winter of despair
 *
 *  % more list.txt 
 *  was it the of 
 * 
 *  % java BlackFilter list.txt < tinyTale.txt 
 *  best times worst times 
 *  age wisdom age foolishness 
 *  epoch belief epoch incredulity 
 *  season light season darkness 
 *  spring hope winter despair 
 *
 ******************************************************************************/

/**
 *  The {@code BlackFilter} class provides a client for reading in a <em>blacklist</em>
 *  of words from a file; then, reading in a sequence of words from standard input, 
 *  printing out each word that <em>does not</em> appear in the file. 
 *  It is useful as a test client for various symbol table implementations.   
 *  <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 BlackFilter {  

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

    public static void main(String[] args) {
        SET<String> set = new SET<String>();

        // read in strings and add to set
        In in = new In(args[0]);
        while (!in.isEmpty()) {
            String word = in.readString();
            set.add(word);
        }

        // read in string from standard input, printing out all exceptions
        while (!StdIn.isEmpty()) {
            String word = StdIn.readString();
            if (!set.contains(word))
                StdOut.println(word);
        }
    }
}


Copyright © 2000–2017, Robert Sedgewick and Kevin Wayne.
Last updated: Fri Oct 20 12:50:46 EDT 2017.