Description

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For this assignment you will have to investigate the use of the Java random number generator function, Math.random(). You can find this in the text or using the online resources given in the lectures.

A Slot Machine Simulation

Understand the Application

What it Looks Like to the User

The program will loop, asking the user for a bet amount from 0 to 50 (assume dollars, you can use ints or longs). If the user types a 0 that means she wants to quit. Otherwise, accept the amount as their bet and simulate a slot machine pull. Your program will print out a line that looks like a slot machine result containing three strings. Some examples are: BAR 7 BAR, 7 7 cherries, cherries BAR space, space BAR BAR, or cherries cherries BAR.

• Each of the three positions in the string could be one of the following: “BAR”, “7”, “cherries” or “space”.

• Each of the three output positions must be generated by your program randomly with probabilities (defined, as always, by final statics):

o BAR (38%)

o cherries (40%)

o space (7%)

o 7 (15%)

o Therefore, cherries should be the most frequent symbol seen and space or 7the least frequent.

• The following combinations should pay the bet as shown (note ORDER MATTERS):

o cherries [not cherries] [any] pays 5 × bet (5 times the bet)

o cherries cherries [not cherries] pays 15 × bet

o cherries cherries cherries pays 30 × bet

o BAR BAR BAR pays 50 × bet

o 7 7 7 pays 100 × bet

• After the pull, display the three strings regardless of the outcome. If the user did not win, tell him/her “Sorry, you lose.” If he won, pay him by displaying his winnings (his original bet times the winning factor from the above table). Then, repeat the whole process by requesting another bet amount.

Position counts! If you read the above bullet that contains the warning “ORDER MATTERS”, you will see that cherries bar cherries pays 5× while cherries cherries bar pays 15× and bar cherries cherries pays nothing.

A Helper Class: TripleString

For this assignment we use our previous class TripleString. You can use your version, with corrections based on my feedback, or my instructor solution. Either way, be sure that it is corrected before incorporating here. I. e., if my instructor solution has any mistakes, you must fix them before using the class here — I don’t think it does, but it might. We will instantiate TripleString objects that can be used in our main() method and/or the static methods that main() invokes to simulate this casino project.

The Static Foothill Methods

Each static Foothill method that you have to write to simulate this casino app plays a special role. For example, there will be one method that gets the bet from the user and returns it to main():

public static int getBet()

Another method will simulate a random pull of the slot machine — it generates three random strings and returns them as a TripleString object to main():

public static TripleString pull()

An output method will be used at the end of each loop-pass when the user needs to see the results of her pull, and receive the news about how much she won (or not):

public static void display (TripleString thePull, int winnings )

We will describe each method — and a few others — in the next section.

The Program Spec

The Foothill Static Method Specs

int getBet()

This prompts the user for input and returns the bet amount as a functional return. It should vet the amount before it returns and insist on a legal bet (0 < bet < 50) until it gets one from the user. This method loops. If any other method is used to test for an illegal value or output an error message based on an illegal value, there will be a 4 point penalty. getBet() must return the legal value to the client and not take any other action besides getting the legal amount.

getBet() has to not only acquire the bet from the user, but also do the output that asks for the bet.

This method must not end the program, but return the valid input result, 0, to the client if/when the user provides it. The client, main() will do what it must when it sees a return value of 0 from this method.

TripleString pull()

This method instantiates and returns a TripleString object to the client. The data of the TripleString object has to first be filled with three randomly chosen strings according to the probabilities described in the “Understand the Application” section above. For example, it might return a TripleString object that contains the three strings [“cherries”, “BAR” , “space”].

The way it determines and loads the three strings is by using a private helper method, described, next, randString(). So this method, pull() will call the next method randString() three times to get the three strings that will be stored into the TripleString object. Once that’s done, pull() just returns the TripleString object to the client and its job is done.

String randString()

This private helper method does a little work — yet is still quite short. It produces and returns a single random string based on the required probabilities. It does this by calling the java Math.random() function and using the return result of that function as a means of deciding which of the four possible strings to return. Take this in stages. Math.random() returns a double between 0 and 1. One idea (but not the only one) is to turn that double into an int between 1 and 1000 using techniques from five weeks ago. Then, decide which of those numbers should trigger a “7”, which should trigger a “cherries”, etc. based on the desired probabilities. Since a “Bar” should happen 38% the time, which numbers would you want to trigger a “Bar”? Since a “cherries” should happen 40% of the time, which numbers would trigger a “cherries”? So you see, this is a very simple — and even short — function, even though it has to be designed carefully. Common sense will go a long way here.

Although this is the only method the requires the constant (finals) that determine the probabilities, those probabilities should be declared as Foothill static finals for easy reference and future changes.

int getPayMultiplier (TripleString thePull)

After main() gets a TripleString object from pull(), which we will call pullString, it needs to know what the payout will be. That’s the job of this function. getPayMultiplier() takes the pullString as a parameter, and inspects it to determine what its pay multiplier should be: 5? 15? 100? 0? It does this by looking at the three strings inside the passed-in TripleString object and using if statements to determine and return the right value. For example, if all three of the strings are “cherries”, which is easily checked using an if statement, then this method returns a pay multiplier of 30. You can use logic like this to create a sequence of if or else ifstatements that will give you the desired multiplier. However you do it, the method will return one of the values; 0, 5, 15, 30, 50 or 100.

void display (TripleString thePull, int winnings )

This method takes the winnings (a dollar amount) and thePull as parameters and displays the three strings inside thePull along with “sorry – you lost ” or “congrats, you won $X.”

Where it All Goes

You can create the TripleString class as a non-public class directly in your client Foothill.java file. You type it directly into that file; do not ask Eclipse to create a new class for you or it will generate a second .java file which we don’t want right now. In other words, Foothill.java will look like this:

import java.util.*;

import java.lang.Math;

public class Foothill

{

// main class stuff …

}

class TripleString

{

// TripleString class stuff …

}

As you see, TripleString is to be defined after, not within, the Foothill class definition. This makes it a sibling class, capable of being used by any other classes in the file (of which there happens to be only one: Foothill).

main()’s Workflow

You can debug each of the above methods individually using a test main() that consists of a statement or two. That way you will make sure each component works before trying to write the final main() client.

main() will be a loop controlled by value returned from getBet(). As long as that value is non-zero, we keep playing.

Each time through the loop, we have to call pull() to get the pullString as a return value. Then we need to pass that to getPayMultiplier() to find the multiplier. We then compute the winnings based on the previous information, and finally we display it all using display(). That’s all that each loop pass does. So main() is quite neat and clean.

Input Errors

The only place the user can make an input error is in getBet(), so that’s the method that deals with such errors. Don’t worry about non-numbers. Assume that an integerwas entered. But do test for range and only return to main after you have a number in the valid range. getBet() may not decide about ending the program. That’s up to main().

Test Run Requirements:

Submit one run that lasts a minimum of 40 pulls, but possibly more (continue reading). At least once enter an illegal amount to make sure that your program handles it correctly. Also, make sure your one run contains both a win of cherries cherries cherries and a win of BAR BAR BAR This may take many runs, but should be accomplished in less than two minutes if your program is written correctly.

General Requirements

Communicate all values as parameters or return values, not through globals (static class variables). The meaning of these terms and examples are contained in the module reading.

Again, getBet() must not only acquire the bet from the user, but also do the output that asks for the bet.

Between your source and your run, report which pull groups that resulted in all cherries and which pulls resulted in all BARs (e.g., “pull groups #33 and #5 resulted in all cherries and pull group #62 resulted in all BARs.” You can type this out in your text file manually after you have pasted the source and run in their correct places.

Also, I will emphasize that in keeping with the separation of I/O and computation, we would not have any method other than display() output results to the screen, and display() is called from main(), not from any other method. Similarly, getBet() is the only method that does input. The other methods do no input, no output and do not call any methods that do input or output. Let’s keep that idea fresh.

Sample Output

Here is an example of a partial run sample (although some numbers and details are not based on the exact requirements, above, and would therefore not receive credit):

// *** I got a pull of all BARS in pull 1 and all cherries in pull 46 ***

/* —————————– sample run ———————————

How much would you like to bet (1 – 50) or 0 to quit? 2