Using Arrays

Classwork

☑ Create a project, and give it a class with a main.

☑ Add a class MadChooser which has an instance variable subjects which is an array of Strings.  We will be filling this up gradually with Strings, so add another instance var to keep track of the first empty position in the array.  We'll leave out accessors and mutators for both of these and not make them available at all outside the class.

☑ In the default constructor for MadChooser, set the array up to be length 20.

☑ Add a method addSubject which takes a String and adds it to the array subjects in the first space that is empty (if there is any space left).  Remember to update the variable for keeping track of the first empty space.

☑ Add a method chooseSubject which chooses and returns a random String from those already added to the array subjects

To choose a random element of the array we can just choose a random index in the array, and then use the element at that index.  Usually that would mean a number from zero up to but not including the length, but we  need it to only include ones that have been added (so up to but not including what number?)  If no words have been added to subjects yet, always return just the String "subject" instead.

☑ Add a toString which returns something like

Subjects (3 words):
dog
cat
diving helmet

showing the number of words that have been added, and a list of those words, but not the unfilled spaces later in the array.

A toString for a class with an array almost always starts by creating a string, adding to it as you loop through the array, and returning a final result at the end.

☑ In a separate class in a main, create a MadChooser, print a randomly chosen subject and the MadChooser itself, then add at least three subjects, print the chooser and a random subject again. (hint: run several times to be sure randomization works)

☑ Add two more methods, addVerb and chooseVerb, for adding Strings and randomly choosing verbs.  If no verbs have been added yet, chooseVerb should just return "verbs".

☑ Update toString  to return something like

Subjects (3 words):
dog
cat
diving helmet

Verbs (2 words):
eats
invents

☑ Also add a constructor that takes  two ints sizeSubject and sizeVerb,  and sets up the arrays to be those sizes instead of size 20.

☑  Add a method chooseSentence which returns a sentence of the form "The S V." Where S is a String returned by chooseSubject() and V is a String returned by chooseVerb().  So if all arrays had nothing added to them, we would get "The subject verbs."  but if words were added we might get "The dog eats" or "The diving helmet invents"

☑ In your main,  add at least 3 verbs to your MadChooser before printing it.  Then, in a loop, generate 10 random sentences with chooseSentence.

☑ In MadChooser add a method addSubjects which takes an array of Strings newSubs as parameter and adds each of the Strings from newSubs to subjects until subjects runs out of room (don't forget that subjects might already have some words in it, and that you can't assume newSubs will be the same length as subjects.  (hint: do you already have a method that adds a word for you, including checking for running out of room?).

☑ In your main, before printing the MadChooser or generating the 10 random sentences, create an array of 5 subject Strings, then use addSubjects to give these to your Madchooser. 

[EC]  Add two more arrays

Add an array to Madchooser for objects, and methods to be able to add individual Strings and choose a random object.  Include the new array in the toString and change chooseSentence to return something of the form "The S V the O" where O is a String returned by chooseObject, so we get sentences like "The dog eats the velociraptor".  Make sure to add some objects in your main. 

  Add another array to Madchooser for adjectives, and arrange to be able to add individual Strings to this new array and choose a random adjective.  Include the new array in the toString and change chooseSentence to return something of the form "The S V the A O" where A is a String returned by chooseAdjective so we get sentences like "The dog eats the enormous velociraptor".  Make sure to add some adjectives in your main.  (You may choose to do adverbs instead.)

(If you do these, you should be able to get some hilarious sentences; feel free to post them to the student discussion board)

[EC] add a constructor to MadChooser which takes arrays of Strings, newSubs and newVerbs.  Set up subjects to be twice the length of newSubs, put the contents of newSubs into subjects, and set the correct first empty spot in subjects.  Do the same for verbs. (hint: a lot of this can be done with things you already wrote, it is always okay to add extra methods if it helps)