GNU Java Training Wheels 2.0: Tutorial 5 A beer drinking song

Question 4.5.1: Study the following code and then compile and run it to verify that it prints out the lyrics to a popular song:

class BeerSong
begin
    beginMain
        System.out.println("Five bottles of beer on the wall.");
        System.out.println("Five bottles of beer on the wall.");
        System.out.println("If one bottle of beer should accidentally fall,");
        System.out.println("there'd be four bottles of beer on the wall.");
        System.out.println();
        System.out.println("Four bottles of beer on the wall.");
        System.out.println("Four bottles of beer on the wall.");
        System.out.println("If one bottle of beer should accidentally fall,");
        System.out.println("there'd be three bottles of beer on the wall.");
        System.out.println();
        System.out.println("Three bottles of beer on the wall.");
        System.out.println("Three bottles of beer on the wall.");
        System.out.println("If one bottle of beer should accidentally fall,");
        System.out.println("there'd be two bottles of beer on the wall.");
        System.out.println();
        System.out.println("Two bottles of beer on the wall.");
        System.out.println("Two bottles of beer on the wall.");
        System.out.println("If one bottle of beer should accidentally fall,");
        System.out.println("There'd be one bottle of beer on the wall.");
        System.out.println();
        System.out.println("One bottle of beer on the wall.");
        System.out.println("One bottle of beer on the wall.");
        System.out.println("If one bottle of beer should accidentally fall,");
        System.out.println("there'd be no bottles of beer on the wall.");
        System.out.println();
    endMain
end

Question 4.5.2: The following is the first attempt to make the code smaller but to keep the same output: If you compile and run the following code you will notice that it counts up from one rather than down from n. Change the for loop so that it runs down rather than up. For information about how to write the for loop, please consult Tutorial 4.2.

class BeerSong
begin
    function song(int n)
    begin
        superfor (var int i=1 to n)
        begin
            System.out.println(i + " bottles of beer on the wall");
            System.out.println(i + " bottles of beer on the wall");
            System.out.println("If one bottle of beer should accidentally fall,");
            System.out.println("there'd be " + (i-1) + " bottles of beer on the wall");
            System.out.println();
        end
    end

    beginMain
        song(5);
    endMain
end

Question 4.5.3: Finish the number2string function below and add a new function call to this function in the song function so that it print textual numbers rather than digits.

function String number2string(int n)
begin
    assert n>=0 : n;
    assert n<=10: n;
    if (n == 0) then return "no";
    if (n == 1) then return "one";
    if (n == 2) then return "two";
    /* rest of code goes here */
    if (n == 9) then return "nine";
    if (n == 10) then return "ten";
    assert false;
end

Question 4.5.4: Add a new function String capitalize(String s) that capitalizes the first word in a String and call this function from the song function so that the first words in each sentence are capitalized. You should find the function Character.toUpperCase and the methods charAt and substring in the package java.lang helpful for writing this function. See the class String in the package java.lang at http://docs.oracle.com/javase/1.5.0/docs/api for more details.

Question 4.5.5: Add new function call String plural(int n) that returns the string "s" if n is not equal to 1 and the empty string "" otherwise. Then call this function from the song function so that the phrase "bottle" is pluralized when it should be.

Question 4.5.6: Write a function called number2string2 that can handle values up to but not including 100. Note that you will need multiple if ... then statements to achieve this. Note that if n is a number then the following expressions are useful:

     var int temp1 = n / 10 % 10 results in temp1 holding the tens digit of n and is zero in the case that n<10.
     var int temp2 = n % 10 results in temp2 holding the ones digit of n.

Question 4.5.7: Change the song function so that the following function call: song(5,"rum"); in the main function results in the following printout:

Five bottles of rum on the wall.

...

there'd be no bottles of rum on the wall.

Question 4.5.8: Once all the code is working, add the following line to the main function: song(100,"gin"); so that it prints out the following:

One hundred bottles of gin on the wall.

...

there'd be zero bottles of gin on the wall.

Question 4.5.9: Write a new function number2string3 that works like number2string2 and number2string except that it handles numbers up to 999. Internally number2string3 should call number2string2. You might find the following function useful:

function String textand(String a, String b)
begin
    if (a.equals("") or b.equals("")) then return a + b;
    else return a + " and " + b;
end

Question 4.5.10: Tricky! Write a new function number2string4 that works like number2string3 execpt that it handles numbers up to nine hundred and ninety-nine million nine hundred and ninety-nine thousand nine hundred and ninety-nine, i.e. 999,999,999. The function number2string4 should internally call number2string3 like so:

4.5 Tutorial 5 A beer drinking song