Goal: Learn how while loops differ from do-while loops.

/// Name: Cornelius Eanes
/// Period: 5
/// Program Name: do-while Swimming
/// File Name: DoWhileSwimming.java
/// Date Finished: Jan 13, 2016

import java.util.Scanner;

public class DoWhileSwimming
{
    public static void main( String[] args ) throws Exception
    {
        Scanner keyboard = new Scanner(System.in);

        String swimmer1 = "GALLANT";
        String swimmer2 = "GOOFUS ";

        double minimumTemperature = 79.0; // degrees Fahrenheit
        double currentTemperature;
        double savedTemperature;
        int swimTime;

        System.out.print("What is the current water temperature? ");
        currentTemperature = keyboard.nextDouble();
        savedTemperature = currentTemperature; // saves a copy of this value so we can get it back later.

        System.out.println( "\nOkay, so the current water temperature is " + currentTemperature + "F." );
        System.out.println( swimmer1 + " approaches the lake...." );

        swimTime = 0;
        while ( currentTemperature >= minimumTemperature )
        {
            System.out.print( "\t" + swimmer1 + " swims for a bit." );
            swimTime++;
            System.out.println( " Swim time: " + swimTime + " min." );
            Thread.sleep(600); // pauses for 600 milliseconds
            currentTemperature -= 0.5; // subtracts 1/2 a degree from the water temperature
            System.out.println( "\tThe current water temperature is now " + currentTemperature + "F." );
        }

        System.out.println( swimmer1 + " stops swimming. Total swim time: " + swimTime + " min." );

        currentTemperature = savedTemperature; // restores original water temperature

        System.out.println( "\nOkay, so the current water temperature is " + currentTemperature + "F." );
        System.out.println( swimmer2 + " approaches the lake...." );

        swimTime = 0;
        do
        {
            System.out.print( "\t" + swimmer2 + " swims for a bit." );
            swimTime++;
            System.out.println( " Swim time: " + swimTime + " min." );
            Thread.sleep(600);
            currentTemperature -= 0.5;
            System.out.println( "\tThe current water temperature is now " + currentTemperature + "F." );

        } while ( currentTemperature >= minimumTemperature );

        System.out.println( swimmer2 + " stops swimming. Total swim time: " + swimTime + " min." );
    }

    // When the input was "80.5", each swimmer swam for 4 minutes.
    // When the input was "78", Gallant swam for 0 minutes, and Goofus swam for 1 minute.
    // Gallant checks the water first before diving in.
    // Goofus, however, dives right in, doesn't check first.
    // A while loop will check whatever's in the conditional first before running the block.
    // A do-while loop, however, will run the block once, and then check the conditional.
    // The while loop is the "pre-test" loop, and the do-while loop is the "post-test" loop.

}

Goal: Modify a program, replacing the while loop with a do-while loop.

/// Name: Cornelius Eanes
/// Period: 5
/// Program Name: Flip Again?
/// File Name: FlipAgain.java
/// Date Finished: Jan 13, 2016

import java.util.Random;
import java.util.Scanner;

public class FlipAgain
{
    public static void main( String[] args )
    {
        Scanner keyboard = new Scanner(System.in);
        Random rng = new Random();

        String again;

        do {
            int flip = rng.nextInt(2);
            String coin;

            if ( flip == 1 )
                coin = "HEADS";
            else
                coin = "TAILS";

            System.out.println( "You flip a coin and it is... " + coin );

            System.out.print( "Would you like to flip again (y/n)? " );
            again = keyboard.next();
        } while (again.equals("y"));

    }
}

Output

Goal: Modify the Roll Doubles program to include a do-while loop.

/// Name: Cornelius Eanes
/// Period: 5
/// Program Name: Dice Doubles
/// File Name: DiceDoubles.java
/// Date Finished: Jan 13, 2016

import java.util.Random;

public class DiceDoubles {

    public static void main(String[] args) {

        Random rand = new Random();
        int r1, r2;

        System.out.println("HERE COMES THE DICE!");

        do {
            r1 = 1 + rand.nextInt(6);
            r2 = 1 + rand.nextInt(6);
            System.out.println();
            System.out.println("Roll #1: " + r1);
            System.out.println("Roll #2: " + r2);
            System.out.println("The total is " + (r1 + r2) + "!");
        } while (r1 != r2);

    }

}

Output

Goal: Modify the Number Guessing with a Counter program to include a do-while loop.

/// Name: Cornelius Eanes
/// Period: 5
/// Program Name: Again with Number Guessing
/// File Name: NumberGuessingAgain.java
/// Date Finished: Jan 13, 2016

import java.util.Random;
import java.util.Scanner;

public class NumberGuessingAgain {

    public static void main(String[] args) {

        Scanner input = new Scanner(System.in);
        Random rand = new Random();
        int correct = 1 + rand.nextInt(10), count = 1, guess;

        System.out.print("I have chosen a random number between 1-10. Guess the number.\n> ");

        do {
            guess = input.nextInt();
            if (guess != correct) {
                System.out.print("Incorrect try again.\n> ");
                count++;
            }
        } while (guess != correct);

        System.out.println("Correct, and it took you " + count + " tries!");

    }

}

Output

Goal: Create a simple calculator with a do-while loop.

/// Name: Cornelius Eanes
/// Period: 5
/// Program Name: Baby Calculator
/// File Name: BabyCalculator.java
/// Date Finished: Jan 13, 2016

import java.util.Scanner;

public class BabyCalculator {

    public static void main( String[] args )
    {
        Scanner keyboard = new Scanner(System.in);

        double a, b, c;
        String op;

        do
        {
            System.out.print("> ");
            a  = keyboard.nextDouble();
            op = keyboard.next();
            b  = keyboard.nextDouble();

            if (op.equals("+")) {
                c = a + b;
            } else if (op.equals("-")) {
                c = a - b;
            } else if (op.equals("*")) {
                c = a * b;
            } else if (op.equals("/")) {
                c = a / b;
            } else if (op.equals("%")) {
                c = a % b;
            } else if (op.equals("^")) {
                c = Math.pow(a, b);
            } else {
                System.out.println("Undefined operator: '" + op + "'.");
                c = 0;
            }

            System.out.println(c);

        } while (a != 0);
    }

}

Output