labexercises2324/week1.java

import java.util.Calendar;
import java.util.Scanner;
import java.util.concurrent.ThreadLocalRandom;

class runLabs {
    public static void main(String[] args) {
        new Lab4();
        new Lab5();
        new Lab6();
    }
}

class Section {
    private int _sectionNumber;

    public Section(int s) {
        this._sectionNumber = s;
        this.printSection();
    }

    public int getSection() {
        return _sectionNumber;
    }

    public void printSection() {
        String title = String.format("Starting section %s", this._sectionNumber);

        System.out.println("-".repeat(title.length()));
        System.out.println(String.format("%s", title));
        System.out.println("-".repeat(title.length()));
    }
}

class Lab {

    public Lab(int lN) {
        String title = String.format("|Starting Lab %s|", lN);
        this._labNumber = lN;

        System.out.println("*".repeat(title.length()));
        System.out.println(title);
        System.out.println("*".repeat(title.length()));
    }

    private int _labNumber;
    public Section currentSection;

    public Section getCurrentSection() {
        return currentSection;
    }

    public void setCurrentSection(Section currentSection) {
        this.currentSection = currentSection;
    }

    public static void printSection(String section) {
        String title = String.format("Starting section %s", section);

        System.out.println("-".repeat(title.length()));
        System.out.println(String.format("%s", title));
        System.out.println("-".repeat(title.length()));
    }

    public int getLabNumber() {
        return this._labNumber;
    }
}

class Lab4 extends Lab {
    public Lab4() {
        super(4);
        ex44();
        ex46();
    }

    // public static void main(String[] args) {
    // }

    public static void ex41() {
        String labSection = "4.1";
        // System.out.println(String.format("Starting section %s", labSection));
        printSection(labSection);

        int testYear1 = 1996; // true
        int testYear2 = 1997; // false
        int testYear3 = 2000; // true
        int testYear4 = 9332; // true
        int testYear5 = 1900; // false

        int randomYear = ThreadLocalRandom.current().nextInt(1, 9999 + 1);

        System.out.println(String.format("Testing %s", testYear1));
        System.out.println(String.format("%s", isLeap(testYear1)));

        System.out.println(String.format("Testing %s", testYear2));
        System.out.println(String.format("%s", isLeap(testYear2)));

        System.out.println(String.format("Testing %s", testYear3));
        System.out.println(String.format("%s", isLeap(testYear3)));

        System.out.println(String.format("Testing %s", testYear4));
        System.out.println(String.format("%s", isLeap(testYear4)));

        System.out.println(String.format("Testing %s", randomYear));
        System.out.println(String.format("%s", isLeap(randomYear)));

        System.out.println(String.format("Testing %s", testYear5));
    }

    public static void ex44() {
        String labSection = "4.4";
        printSection(labSection);

        // System.out.println("------------------------");
        // System.out.println("Starting lab section " + labSection);
        // System.out.println("------------------------");

        String month1 = "oct";
        int year1 = 2000;
        System.out.println(String.format("Month: %s\tYear: %d\tDays in month: %d",
                                         month1, year1, monthLen(month1, year1)));

        String month2 = "feb";
        int year2 = 2000;
        System.out.println(String.format("Month: %s\tYear: %d\tDays in month: %d",
                                         month2, year2, monthLen(month2, year2)));

        String month3 = "feb";
        int year3 = 1997;
        System.out.println(String.format("Month: %s\tYear: %d\tDays in month: %d",
                                         month3, year3, monthLen(month3, year3)));

        String month4 = "apr";
        int year4 = 2001;
        System.out.println(String.format("Month: %s\tYear: %d\tDays in month: %d",
                month4, year4, monthLen(month4, year4)));

    }

    /**
     * Lab section 4.5
     *
     * Write a program that can calculate how many whole years old someone is from
     * today’s date and their date of birth. You could store each date as three
     * integers (day,
     * month, year)
     */
    public static void ex46() {
        String labSection = "4.6";
        printSection(labSection);
        // calculate whole years' old to date

        Calendar today = Calendar.getInstance();
        System.out.println("Today:\t" + today.getTime());

        Calendar dob1 = Calendar.getInstance();
        dob1.set(1990, 1, 1);

        System.out.println(String.format(
                "DOB 1:\t%s (difference:\t%d years)",
                                         dob1.getTime(),
                                         yearDifference(today, dob1)));

        Calendar dob2 = Calendar.getInstance();
        dob2.set(1994, 12, 22);

        System.out.println(String.format(
                "DOB 2:\t%s (difference:\t%d years)",
                                         dob2.getTime(),
                                         yearDifference(today, dob2)));
    }

    public static boolean isLeap(int year) {
        if (year % 4 != 0) {
            return false;
        } else {
            if (year % 100 == 0) {
                if (year % 400 == 0) {
                    return true;
                } else {
                    return false;
                }
            }
            return true;
        }
    }

    public static int monthLen(String month, int year) {
        if (month == "feb") {
            if (isLeap(year)) {
                return 29;
            } else {
                return 28;
            }
        } else if (
            (month == "apr") ||
            (month == "jun") ||
            (month == "sep") ||
            (month == "nov")) {
                return 30;
        } else {
            return 31;
        }
    }

    public static int yearDifference(Calendar date1, Calendar date2)
    {
        return (int) Math.abs(date1.get(Calendar.YEAR) -
                              date2.get(Calendar.YEAR)
                              );
    }
}

/**
 * Keyboard input
 */
class Lab5 extends Lab {
    public Lab5() {
        super(5);
        new five1();
    }

    class five1 extends Section {
        /**
         * We will now look at how we can get user input from the keyboard. We will
         * gloss over some
         * of the details here, but give you just the information you need to start
         * getting input and
         * processing it.
         */
        public five1() {
            super(1);
            System.out.println(String.format("TBC"));
            // Scanner keyboard = new Scanner(System.in);
            // System.out.println("Please enter your name, followed by the return key?");
            // String userEntry = keyboard.nextLine();
            // System.out.println("Hello " + userEntry);
            // System.out.println(String.format("%s", keyboard));
        }
    }
}

/**
 * Loops
 */
class Lab6 extends Lab {
    public Lab6() {
        super(6);
        new six1();
        System.out.println(String.format("%n"));
        new six3();
        new six5();
        new six6();
        new six7();
    }

    /**
     * Times tables
     */
    class six1 extends Section {
        public six1() {
            super(1);
            int testNum = 6;
            System.out.println(String.format("Times table for %d:", testNum));
            writeTimesTable(7);
        }
    }

    class six3 extends Section {
        public six3() {
            super(3);
            int testNum = 13; // statistically the most prime of all numbers
            System.out.println(String.format("Testing primes..."));
            System.out.println(String.format("%d prime? %s", testNum, isPrime(testNum)));
            System.out.println(String.format("%d prime? %s", 23, isPrime(23)));
            System.out.println(String.format("%d prime? %s", 27, isPrime(27)));
            System.out.println(String.format("%d prime? %s", 28, isPrime(28)));
            System.out.println(String.format("%d prime? %s", 299, isPrime(299)));
            System.out.println(String.format("Generating primes..."));
            generatePrimes(1024);
            System.out.println(String.format("Done!%n"));
        }
    }

    class six5 extends Section {
        public six5() {
            super(5);
            System.out.println(String.format("TODO / NOT IMPLEMENTED until we get stdin working"));
        }
    }
    /**
     * Produce a number triangle
     *
     * eg:
     *    1
     *   2 2
     *  3 3 3
     * 4 4 4 4
     */
    class six6 extends Section {
        public six6() {
            super(6);
            numberTriangle(1);
            numberTriangle(4);
            numberTriangle(8);
            numberTriangle(29);
        }
    }

    class six7 extends Section {
        public six7() {
            super(7);
            describeDD(4.2, 1.6);
            describeDD(47.42, 7.9);
        }

        /** Simple exposition of double division
         * @param num1 Dividend
         * @param num2 Divisor
         */
        public void describeDD(double num1, double num2) {
            System.out.println(String.format("Double division of %.2f by %.2f:\t", num1, num2));
            DoubleDivisionResult result = doubleDivision(num1, num2);
            System.out.println(String.format("Quotient: %d (ie %.2f ✕ %d = %.2f)\tRemainder: %.2f",
                                             result.getQuotient(),
                                             num2,
                                             result.getQuotient(),
                                             (num2 * result.getQuotient()),
                                             result.getRemainder()));
        }
    }

    /* TOASK - is there a better way of returning multiple values in Java?
       à la python, ie: return (quotient, remainder)
    */

    /**
     * Wrapper class for returning results from double division
     */
    final class DoubleDivisionResult {
        private int quotient; // that's the number of times something goes into something else
        private double remainder; // that's the bit left over

        public DoubleDivisionResult(int quotient, double remainder) {
            this.quotient = quotient;
            this.remainder = remainder;
        }

        public int getQuotient() {
            return quotient;
        }

        public double getRemainder() {
            return remainder;
        }

    }

    /**
     * Perform 'double division'
     *
     * @param dividend Number to be divided
     * @param divisor Number to divide by
     * @return a {@link DoubleDivisionResult} with the (int) quotient and (double) remainder
     */
    public DoubleDivisionResult doubleDivision(double dividend, double divisor) {
        // example used is 4.2 and 1.6
        // should return 2 and 1.0
        final boolean DEBUG = false;
        double dQuotient = dividend / divisor;
        int iQuotient = (int)dQuotient;

        double remainder = dividend - (iQuotient * divisor);

        if (DEBUG) {
            System.out.println(String.format("float quotient: %.2f", dQuotient));
            System.out.println(String.format("int quotient: %d", iQuotient));
            // TOASK: is there a neater way to do this casting?
        }

        return new DoubleDivisionResult(iQuotient, remainder);
    }

    /**
     * @param num Size of triangle
     */
    public void numberTriangle(int num) {
        /* Observations:
           - for even-sized triangles, preceding number of spaces starts at n=rows and decrements
           - for even-sized triangles even numbers have odd spaces and vice versa
        */
        System.out.println(String.format(""));
        int spaces = num;
        for (int i = 1; i <= num; i++) {
            System.out.println(" ".repeat(spaces)
                               + String.format("%s ", i).repeat(i)
                               + " ".repeat(spaces-1)
                               );
            spaces--;
        }
        System.out.println(String.format(""));
    }

    /**
     * @param num The number to write the times table for
     * @param limit How many multiples to show
     */
    public void writeTimesTable(int num, int limit) {
        for (int i = 0; i < (limit + 1); i++) {
            System.out.printf("%d\t", num * i);
        }
    }

    /* TOASK - overload example.
       Question: is there a better way of doing optional function parameters in java?
    */
    /**
     * Write times table for num (10 entries)
     * @param num Number to show times table for
     */
    public void writeTimesTable(int num) {
        int DEFAULT_LIMIT = 10;
        writeTimesTable(num, DEFAULT_LIMIT);
    }

    public void generatePrimes(int upperLimit) {
        // handle 2 as a special case
        System.out.println(String.format("2"));
        // for (int i = 3; i <= upperLimit; i += 2) {
        for (int i = 2; i <= upperLimit; i++) {
            // TODO: figure out smarter way of doing this, I'm sure primes must be at least 6 apart...
            // Something about 2n ± 1 ?
            // seive of Erasthotenes ..?
            if (isPrime(i)) {
                System.out.printf("%d\t", i);
            }
        }
    }

    /**
     * But is it prime?
     * @param  num Integer to test for primality
     * @return if it's prime
     */
    public boolean isPrime(int num) {
        boolean DEBUG = false;
        if ((num == 2) || (num == 1)) {
            return true;
        }
        if (num % 2 == 0){
            return false;
        } else {
            int divisor = 3;
            double numSquareRoot = Math.sqrt((double)num);
            while (divisor <= numSquareRoot) {
                if (num % divisor == 0) {
                    return false;
                }
                divisor += 2;
                if (DEBUG) {
                    System.out.printf("%d\t", divisor);
                }
            }
            return true;
        }
    }
}