Counter.java

Below is the syntax highlighted version of Counter.java.

/******************************************************************************
 *  Compilation:  javac Counter.java
 *  Execution:    java Counter n trials
 *  Dependencies: StdRandom.java StdOut.java
 *
 *  A mutable data type for an integer counter.
 *
 *  The test clients create n counters and performs trials increment
 *  operations on random counters.
 *
 * java Counter 6 600000
 *  100140 counter0
 *  100273 counter1
 *  99848 counter2
 *  100129 counter3
 *  99973 counter4
 *  99637 counter5
 *
 ******************************************************************************/

package edu.princeton.cs.algs4;

/**
 *  The {@code Counter} class is a mutable data type to encapsulate a counter.
 *  <p>
 *  For additional documentation,
 *  see <a href="https://algs4.cs.princeton.edu/12oop">Section 1.2</a> of
 *  <i>Algorithms, 4th Edition</i> by Robert Sedgewick and Kevin Wayne.
 *
 *  @author Robert Sedgewick
 *  @author Kevin Wayne
 */
public class Counter implements Comparable<Counter> {

    private final String name;     // counter name
    private int count = 0;         // current value

    /**
     * Initializes a new counter starting at 0, with the given id.
     *
     * @param id the name of the counter
     */
    public Counter(String id) {
        name = id;
    }

    /**
     * Increments the counter by 1.
     */
    public void increment() {
        count++;
    }

    /**
     * Returns the current value of this counter.
     *
     * @return the current value of this counter
     */
    public int tally() {
        return count;
    }

    /**
     * Returns a string representation of this counter.
     *
     * @return a string representation of this counter
     */
    public String toString() {
        return count + " " + name;
    }

    /**
     * Compares this counter to the specified counter.
     *
     * @param  that the other counter
     * @return {@code 0} if the value of this counter equals
     *         the value of that counter; a negative integer if
     *         the value of this counter is less than the value of
     *         that counter; and a positive integer if the value
     *         of this counter is greater than the value of that
     *         counter
     */
    @Override
    public int compareTo(Counter that) {
        return Integer.compare(this.count, that.count);
    }


    /**
     * Reads two command-line integers n and trials; creates n counters;
     * increments trials counters at random; and prints results.
     *
     * @param args the command-line arguments
     */
    public static void main(String[] args) {
        int n = Integer.parseInt(args[0]);
        int trials = Integer.parseInt(args[1]);

        // create n counters
        Counter[] hits = new Counter[n];
        for (int i = 0; i < n; i++) {
            hits[i] = new Counter("counter" + i);
        }

        // increment trials counters at random
        for (int t = 0; t < trials; t++) {
            hits[StdRandom.uniformInt(n)].increment();
        }

        // print results
        for (int i = 0; i < n; i++) {
            StdOut.println(hits[i]);
        }
    }
}

/******************************************************************************
 *  Copyright 2002-2022, Robert Sedgewick and Kevin Wayne.
 *
 *  This file is part of algs4.jar, which accompanies the textbook
 *
 *      Algorithms, 4th edition by Robert Sedgewick and Kevin Wayne,
 *      Addison-Wesley Professional, 2011, ISBN 0-321-57351-X.
 *      http://algs4.cs.princeton.edu
 *
 *
 *  algs4.jar is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  algs4.jar is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with algs4.jar.  If not, see http://www.gnu.org/licenses.
 ******************************************************************************/