Algorithm notes on the back of used envelopes bound in a ring binder

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello, World");
    }
}

public class HelloGoodbye {
    public static void main(String[] args) {
        System.out.println("Hello " + args[0] + " and " + args[1] + ".");
        System.out.println("Goodbye " + args[1] + " and " + args[0] + ".");
    }
}

import edu.princeton.cs.algs4.StdIn;
import edu.princeton.cs.algs4.StdOut;
import edu.princeton.cs.algs4.StdRandom;

public class RandomWord {
    public static void main(String[] args) {
        int idx = 1;
        String champ = "";
        while (!StdIn.isEmpty()) {
            String word = StdIn.readString();
            double odds = 1.0D / idx;
            boolean isWinner = StdRandom.bernoulli(odds);
            if (isWinner) {
                champ = word;
            }
            idx++;
        }
        StdOut.println(champ);
    }
}

coursera/src$ zip -r hello.zip HelloGoodbye.java HelloWorld.java RandomWord.java
updating: HelloGoodbye.java (deflated 44%)
updating: HelloWorld.java (deflated 19%)
updating: RandomWord.java (deflated 65%)

coursera/src$ CLASSPATH=../algs4.jar javac RandomWord.java
coursera/src$ CLASSPATH=.:../algs4.jar java RandomWord
# in my environment, `while (!StdIn.isEmpty())` didn't stop

The following code was not allowed.

Checkstyle ends with 5 errors.
[ERROR] RandomWord.java:6:5: Do not declare instance variables in this program. [NothingButMain]
[ERROR] RandomWord.java:7:5: Do not declare instance variables in this program. [NothingButMain]
[ERROR] RandomWord.java:9:5: Do not define instance methods in this program. [NothingButMain]
[ERROR] RandomWord.java:18:5: Do not define instance methods in this program. [NothingButMain]
[ERROR] RandomWord.java:38:25: Do not create arrays (or other objects) with 'new' in this program. [Design]

/**
 * RandomWordSelector selects one of the words, which are fed sequentially, in a real-time manner.
 */
class RandomWordSelector {
    private int consumptionCount;
    private String selection;

    public void consume(String word) {
        double odds = 1.0D / (consumptionCount + 1);
        boolean retain = StdRandom.bernoulli(odds);
        if (retain) {
            selection = word;
        }
        consumptionCount++;
    }

    public String getSelection() {
        return selection;
    }
}

public class RandomWord {
    public static void main(String[] args) {
        RandomWordSelector rws = new RandomWordSelector();
        while (!StdIn.isEmpty()) {
            rws.consume(StdIn.readString());
        }
        StdOut.println(rws.getSelection());
    }
}