Week 2 Homework Solutions

WeekTwoHW.java

/**
 * This class contains the solutions to
 * the Week 2 homework exercises.
 */
public class WeekTwoHW {

    public static void main(String[] args) {

        // -------- MANDATORY PROBLEMS --------

        /*
        Problem 1. Write a Java program to declare three variables:
        bananas, budget, and cost and store the values 10, 20.3, and
        3.14785, respectively.
         */

        int bananas = 10; // integer because you cannot have part of a banana
        double budget = 20.3; // budget & cost must be decimal numbers
        double cost = 3.14785;

        System.out.println("--- MANDATORY PROBLEMS ---");
        System.out.println("\nProblem 1:\n");
        System.out.println("\tBananas: " + bananas);
        System.out.println("\tBudget: " + budget);
        System.out.println("\tCost: " + cost);

        /*
        Problem 2: Write a Java program to declare a Boolean variable
        with initial value of “true.” Change it to “false” before printing it.
         */

        boolean bool = true; // you can name your boolean variable anything
        bool = false;

        System.out.println("\nProblem 2:\n");
        System.out.println("\tBoolean value: " + bool);

        /*
        Problem 3: Write a Java program to convert minutes into a number of days and years.
        Hint: make 3 integer variables that store the number of minutes, days, and years
         */

        // CONSTANTS - optional variables
        final int min_per_hr = 60;
        final int hrs_per_day = 24;
        final int days_per_yr = 365;

        // MINUTES TO DAYS:
        //           1 hr    1 day
        //  M min x ------ x ------
        //          60 min   24 hrs

        // MINUTES TO YEARS:
        //           1 hr    1 day     1 yr
        //  M min x ------ x ------ x -------
        //          60 min   24 hrs   365 days

        double minutes = 525600*4; // change the number here to see what happens

        double hrs = minutes / min_per_hr; // optional variable

        double days = hrs / hrs_per_day;
        double years = days / days_per_yr;

        System.out.println("\nProblem 3:\n");
        System.out.println("\tMinutes: " + minutes);
        System.out.println("\tDays: " + days);
        System.out.println("\tYears: " + years);

        // -------- OPTIONAL PROBLEMS --------

        /*
        Problem 1: Write a Java program that takes two variables, a and b, and
        then prints the sum, the difference, the product, the average, the distance
        (the difference between integer), the maximum (the larger of the two integers),
        the minimum (smaller of the two integers). You should have variables that will
        store each answer.

        NOTE: There can be alternate solutions to these problems
         */

        // try changing the numbers to see what happens
        double a = 12;
        double b = 18;

        double sum = a + b;
        double diff = a - b;
        double avg = sum / 2; // (a + b)/2 is also correct

        double dist = Math.abs(diff); // b - a is also correct
        double max = Math.max(a, b); // b is also correct
        double min = Math.min(a, b); // a is also correct

        // Math.abs() is a method from Java that gives you the absolute value
        // of a number. If -1 is passed in, it returns 1. If 4 is passed in,
        // it returns 4. It turns a negative number into a positive one.
        // More info here: https://www.w3schools.com/java/ref_math_abs.asp

        // Math.max() is a method from Java that gives you the larger of two numbers.
        // More info here: https://www.w3schools.com/jsref/jsref_max.asp

        // Math.min() is a method from Java that gives you the smaller of two numbers.
        // More info here: https://www.w3schools.com/jsref/jsref_min.asp

        System.out.println("\n--- OPTIONAL PROBLEMS ---");
        System.out.println("\nProblem 1:\n");
        System.out.println("\tSum: " + sum);
        System.out.println("\tDifference: " + diff);
        System.out.println("\tAverage: " + avg);
        System.out.println("\tDistance: " + dist);
        System.out.println("\tMaximum: " + max);
        System.out.println("\tMinimum: " + min);

        /*
        Problem 2: Write a Java program to break an integer into a
        sequence of individual digits (example: 54321 to 5 4 3 2 1)

        NOTE: Assume it will ALWAYS ask for a 5 digit number
         */

        // Try entering another 5 digit number to see what happens
        int num1 = 54321;

        int ones = num1 % 10; // 1
        System.out.println("\nProblem 2:\n");
        System.out.println("\tOnes digit: " + ones);

        int num2 = num1 / 10; // 5432.1 will be cut down to 5432

        int tenth  = num2 % 10; // 2
        System.out.println("\tTenth digit: " + tenth);

        int num3 = num2 / 10; // 543.2 will be cut down to 543

        int hundredth  = num3 % 10; // 3
        System.out.println("\tHundredth digit: " + hundredth);

        int num4 = num3 / 10; // 54.3 will be cut down to 54

        int thousandth = num4 % 10; // 4
        System.out.println("\tThousandth digit: " + thousandth);

        int num5 = num4 / 10; // 5.4 will be cut down to 5

        int ten_thousandth = num5 % 10; // 5
        System.out.println("\tTen Thousandth digit: " + ten_thousandth);

    }

}