Question

LAB PROMPT:

Lab 07

Hello future bakers and artisans of the fine gourmet. You love to throw parties, and what goes better at a party than cake! The problem is that you only have enough flour to bake a limited number of cakes. In this lab, you will write a small program to figure out if you have enough flour to bake the number of cakes needed for the people attending.

Step 1 - using final

At the top of your class, you should declare the following variables as static and final

• CUPS_FLOUR_PER_CAKE
  Initialize it in the same line to 2.3. As such, it should be a double.
• PIECES_PER_CAKE
  Initialize it to 8. As such, it should be an int.
• NOT_ENOUGH_FLOUR
  Initialize it to -1
• EXACT_CAKE
  Initialize it to 0
• EXTRA_CAKE
  Initialize it to 1

here an example of declaring the first one to give you an idea:

static final double CUPS_FLOUR_PER_CAKE = 2.3;

These variables are final / constants (meaning you can’t change them) and are available at the class level. This last part means every method in the class has access to them and can be used in every method!

To test this, go to your main, and put in the following code:

System.out.println(CUPS_FLOUR_PER_CAKE);
System.out.println(PIECES_PER_CAKE);

Run your program, and it should simply print 2.3 and 8 to the console.

Step 2 - calcNumCakesBaked

For this step you will write the method calcNumCakesBaked. Here are some important things you need to know before writing this method

• Math.floor
  Math.floor takes in a double value, and returns whole number portion. It is a static method in the Math object. For example, if I put in Math.floor(10.6) it will return 10.0. If I put in Math.floor(10.1) it would also return 10.0. Notice it is returning a double.
• Casting
  Sometimes you want to convert a double to an int. As there is a loss of precision (the decimals), you have explicitly state you want to do that. As such, you use (int) for example, (int)3.14 returns the int 3 (notice no decimal point).

Write calcNumCakesBaked

Now go to the method section of your file, and write a public static method
called calcNumCakesBakes that returns an int. It takes in a double in the parameter that represents the number of cupsOnHand. For example the method signature could look like this:

public static int calcNumCakesBaked(double cupsOnHand)

Inside the method you need to do the following:

1) It needs to return - as a whole number - the number of possible cakes one can build based on the cups of flour the baker has on hand.

• cupsOnHand is the amount of flour the baker has

• CUPS_FLOUR_PER_CAKE tells you how many cups it takes to bake a cake

• As such, the formula to figure out how many cakes you can bake is:

  cakes = cupsOnHand / CUPS_FLOUR_PER_CAKE

• You must declare cakes as a variable of type int inside your method.

2) The problem - you have to return an int, rounded down that represents the number of cakes. Use the Math.floor method, and casting to help you with that.

Test calcNumCakesBaked

Always test each method after writing (ideally while writing). So go down to your main method, and put in the following tests:

System.out.println("#### Testing calcNumCakesBaked");
System.out.println(calcNumCakesBaked(0));
System.out.println(calcNumCakesBaked(2.3));
System.out.println(calcNumCakesBaked(3));
System.out.println(calcNumCakesBaked(42));

Now double check the output. Is it what you think it should be?

Step 3 - getCakeEnthusiasts

There is a little known fact, that no matter how large of the party, only a max of 19 people want cake. This “fact” is even stranger, the number is actually based the remainder of the total guests at a party divided by 20. So if there are 100 guests, no one wants cake, but if there are 117 guests 17 of them want cake. Ok, we made it up, to give you practice with modulo, but let’s get this party started.

• % operator - as a quick reminder, the modulo operator returns the remainder of a long division. If you have 17, and you divide by 10, the remainder would be 7. Written in java, that would be 17 % 10. Extra tutorial.

Write getCakeEnthusiasts

The public static method getCakeEnthusiasts returns an int. It also needs the parameter of type int that represents the number of party goers (e.g. partySize) to work. What would that method signature look like?

Using the partySize, simply mod it (%) by 20, and return the answer.

Test getCakeEnthusiasts

Go to your main, and add the following tests:

System.out.println("#### Testing getCakeEnthusiasts ####");
System.out.println(getCakeEnthusiasts(21));
System.out.println(getCakeEnthusiasts(3));
System.out.println(getCakeEnthusiasts(20));
System.out.println(getCakeEnthusiasts(42));
System.out.println(getCakeEnthusiasts(100000001));

Did the results come out as you expected?

Step 4 - getMessage

It is very common in applications to have a method return a message based on a message ‘type’ passed to it. This allows for easy language integrations, and one place to change the messages. This method follows the same model with three messages. You will pass in an int value (the message type), and return one of three possible messages.

Write getMessage

You will write a public static method called getMessage that returns a String. The method will have a single int parameter that represents the message type. What would the signature look like?

Now you will have the method signature return a message String based on the type, as follows:

• Sorry. You do not have enough flour to bake a cake.
  Message Type: anything less than 0
• No left over cake.
  Message Type: equal to 0
• Yay, left over cake!
  Message Type: anything greater than 0

You will notice there are only three message types: less than 0, 0, or greater than 0. This is fairly common in programming.

Test getMessage

You just wrote three to four lines of code - time to test again! Put the following into your main method, and run the program. Did you get what you expected?

System.out.println("### TESTING getMessage ###");
System.out.println(getMessage(-1));
System.out.println(getMessage(0));
System.out.println(getMessage(1));

Step 5 - determineLeftoverCake

This method wants to look at the total number of cakes you can bake and compare it to the number of folks at the party who want cake. Based on the answer, you will return NOT_ENOUGH_FLOUR, EXACT_CAKE, or EXTRA_CAKE.

This method will use:

• complex logic
  Both || and &&

Write determineLeftoverCake

determineLeftoverCake is a public static method that returns an int value which is either NOT_ENOUGH_FLOUR, EXACT_CAKE, or EXTRA_CAKE. For the method to work, you will need both the number of people, and the number of cakes. Putting that together, our method signature could look like:

 public static int determineLeftoverCake(int cakes, int people) 

The first thing you will want to do is determine the number of pieces of cake. This is done by multiplying the PIECES_PER_CAKE times the number of cakes. We called the answer variable numPiecesCake.

You will then write the following conditions:

• if cakes is less than or equal to 0 or numPiecesCake is less than people, return NOT_ENOUGH_FLOUR.
• if people is greater than 0 and the numPiecesCake minus the number of people is 0, return EXACT_CAKE
• Lastly, it means you have more than enough cake, so return EXTRA_CAKE

Test determineLeftoverCake

You wrote a few more lines of code, it is best to test it. Put the following in your main method

System.out.println("### Testing determineLeftoverCake ###");
System.out.println(determineLeftoverCake(10, 10));
System.out.println(determineLeftoverCake(10, 80));
System.out.println(determineLeftoverCake(0, 9));
System.out.println(determineLeftoverCake(1, 8));

Is it returning what you think it should?

Step 6 - Gluing it together!

Go ahead and uncomment the randomTests method, and the method call to randomTests in main.

PROVIDED CODE:

import java.util.Random;

public class BakerHelper {
public static final Random RND = new Random(); // do not modify, but use as an example of a class variable

// declare your class-level variables here


// declare your methods here



public static void main(String[] args) {
// add your own tests here
  
  
// randomTests(); // uncomment when mostly done
}

/*remove-when-ready
static void randomTests() {
for(int i = 0; i < 20; i++) {
System.out.println(getMessage(determineLeftoverCake(calcNumCakesBaked(getCupsOnHand()),
getCakeEnthusiasts(getRSVP()))));
}
}
end-comment*/

// ************** don't modify below this line ************************
/**
* Gets a random number of people who are attending the party
* @returns random whole number from 0-99 of party goers
**/
public static int getRSVP() {
return RND.nextInt(100);
}

/**
* Gets a random number of cups of flour to see how much to have
* @returns random double number between 0-9
**/
public static double getCupsOnHand() {
return RND.nextInt(10) + RND.nextDouble();
}
  
}

Answer 1

Below is the code in JAVA for the above question:

import java.util.Random;

//BakerHelper class
public class BakerHelper {

   public static final Random RND = new Random(); // do not modify, but use as an example of a class variable

   // declare your class-level variables here
   static final double CUPS_FLOUR_PER_CAKE = 2.3;
   static final double PIECES_PER_CAKE = 8;
   static final double NOT_ENOUGH_FLOUR = -1;
   static final double EXACT_CAKE = 0;
   static final double EXTRA_CAKE = 1;

   // declare your methods here
   //created method calcNumCakesBaked
   public static int calcNumCakesBaked(double cupsOnHand) {
       int cakes;
       cakes = (int) (Math.floor(cupsOnHand / CUPS_FLOUR_PER_CAKE));
       return cakes;
   }
   //created method getCakeEnthusiasts
   public static int getCakeEnthusiasts(int partySize) {
       int size = partySize % 20;
       return size;
   }
   //created method getMessage
   public static String getMessage(int messageType) {
       String message = null;
       if (messageType < 0)
           message = "Sorry. You do not have enough flour to bake a cake.";
       else if (messageType == 0)
           message = "No left over cake.";
       else if (messageType > 0)
           message = "Yay, left over cake!";
       return message;
   }
   //created method determineLeftoverCake
   public static int determineLeftoverCake(int cakes, int people) {
       int numPiecesCake;
       numPiecesCake = (int) (cakes * PIECES_PER_CAKE);
       if (cakes <= 0 || numPiecesCake < people)
           return (int) NOT_ENOUGH_FLOUR;
       else if (people > 0 && (numPiecesCake - people == 0))
           return (int) EXACT_CAKE;
       else
           return (int) EXTRA_CAKE;
   }

   public static void main(String[] args) {
       // add your own tests here
       //testing each method.
       System.out.println(CUPS_FLOUR_PER_CAKE);
       System.out.println(PIECES_PER_CAKE);
      
       System.out.println("#### Testing calcNumCakesBaked");
       System.out.println(calcNumCakesBaked(0));
       System.out.println(calcNumCakesBaked(2.3));
       System.out.println(calcNumCakesBaked(3));
       System.out.println(calcNumCakesBaked(42));
      
       System.out.println("#### Testing getCakeEnthusiasts ####");
       System.out.println(getCakeEnthusiasts(21));
       System.out.println(getCakeEnthusiasts(3));
       System.out.println(getCakeEnthusiasts(20));
       System.out.println(getCakeEnthusiasts(42));
       System.out.println(getCakeEnthusiasts(100000001));
      
       System.out.println("### TESTING getMessage ###");
       System.out.println(getMessage(-1));
       System.out.println(getMessage(0));
       System.out.println(getMessage(1));
      
       System.out.println("### Testing determineLeftoverCake ###");
       System.out.println(determineLeftoverCake(10, 10));
       System.out.println(determineLeftoverCake(10, 80));
       System.out.println(determineLeftoverCake(0, 9));
       System.out.println(determineLeftoverCake(1, 8));

       //uncommented the calling method
       randomTests(); // uncomment when mostly done
   }

   static void randomTests() {
       for (int i = 0; i < 20; i++) {
           System.out.println(getMessage(
                   determineLeftoverCake(calcNumCakesBaked(getCupsOnHand()), getCakeEnthusiasts(getRSVP()))));
       }
   }
  
   // ************** don't modify below this line ************************
   /**
   * Gets a random number of people who are attending the party
   *
   * @returns random whole number from 0-99 of party goers
   **/
   public static int getRSVP() {
       return RND.nextInt(100);
   }

   /**
   * Gets a random number of cups of flour to see how much to have
   *
   * @returns random double number between 0-9
   **/
   public static double getCupsOnHand() {
       return RND.nextInt(10) + RND.nextDouble();
   }
}

Refer to the screenshot attached below to better understand the code and indentation:

1 import java.util. Random; 3 //BakerHelper class public class BakerHelper { public static final Random RND = new Random(); // do not modify, but use as an example of a class variable WOOWN // declare your class-level variables here static final double CUPS_FLOUR_PER_CAKE = 2.3; static final double PIECES_PER_CAKE = 8; static final double NOT ENOUGH FLOUR = -1; static final double EXACT_CAKE = 0; static final double EXTRA_CAKE = 1; 170 // declare your methods here //created method calcNumCakes Baked public static int calcNumCakesBaked (double cupsOnHand) { int cakes; cakes = (int) (Math.floor(cups On Hand / CUPS_FLOUR_PER_CAKE)); return cakes; 22 230 //created method getCakeEnthusiasts public static int getCake Enthusiasts(int partySize) { int size = partySize % 20; return size; 24 25 //created method getMessage public static String getMessage(int messageType) { String message = null; if (messageType < 0) message = "Sorry. You do not have enough flour to bake a cake."; else if (messageType == 0) message = "No left over cake."; else if (messageType > 0) message = "Yay, left over cake!"; return message;


38 39e //created method determineLeftoverCake public static int determineLeftoverCake(int cakes, int people) { int numPiecesCake; numPiecesCake = (int) (cakes * PIECES_PER_CAKE); if (cakes <= 0 || numPiecesCake < people) return (int) NOT_ENOUGH_FLOUR; else if (people > 0 && (numPiecesCake - people == 0)) return (int) EXACT_CAKE; else return (int) EXTRA_CAKE; public static void main(String[] args) { // add your own tests here //testing each method. System.out.println(CUPS_FLOUR_PER_CAKE); System.out.println(PIECES_PER_CAKE); System.out.println("#### Testing calcNumCakesBaked"); System.out.println(calcNumCakesBaked()); System.out.println(calcNumCakesBaked (2.3); System.out.println(calcNumCakesBaked (3)); System.out.println(calcNumCakesBaked (42)); System.out.println("#### Testing getCakeEnthusiasts ####"); System.out.println(getCakeEnthusiasts(21)); System.out.println(getCakeEnthusiasts(3)); System.out.println(getCakeEnthusiasts (20)); System.out.println(getCakeEnthusiasts(42)); System.out.println(getCakeEnthusiasts(100000001)); System.out.println("### TESTING getMessage #*#"); System.out.println(getMessage(-1)); System.out.println(getMessage()); System.out.println(getMessage(1));


System.out.println("### Testing determineLeftoverCake ###"); System.out.println(determineLeftoverCake (10, 10)); System.out.println(determineLeftoverCake (10, 80)); System.out.println(determine LeftoverCake (O, 9)); System.out.println(determineLeftoverCake(1, 8)); //uncommented the calling method randomTests(); // uncomment when mostly done static void randomTests() { for (int i = 0; i < 20; i++) { System.out.println(getMessage determineLeftoverCake (calcNumCakesBaked(getCupsonHand(), getCakeEnthusiasts(getRSVP )))); // ************** don't modify below this line ******* /** * Gets a random number of people who are attending the party * @returns random whole number from 6-99 of party goers * public static int getRSVP() { return RND.nextInt(100); 99 100 1010 /** * Gets a random number of cups of flour to see how much to have 102 103 104 105 1060 107 108 109} * @returns random double number between 0-9 *** public static double getCupsOnHand() { return RND.nextInt(10) + RND.nextDouble();


Output:

2.3 8.0 #### Testing calcNumCakesBaked #### Testing getCake Enthusiasts #### ### TESTING getMessage ### Sorry. You do not have enough flour to bake a cake. No left over cake. Yay, left over cake! ### Testing determineLeftoverCake ###


Yay, left over cake! Yay, left over cake! Yay, left over cake! Yay, left over cake! Yay, left over cake! Sorry. You do not have enough flour to bake a cake. Yay, left over cake! Sorry. You do not have enough flour to bake a cake. Sorry. You do not have enough flour to bake a cake. Yay, left over cake! Yay, left over cake! Sorry. You do not have enough flour to bake a cake. Yay, left over cake! Yay, left over cake! Yay, left over cake! Yay, left over cake! Sorry. You do not have enough flour to bake a cake. Sorry. You do not have enough flour to bake a cake. Sorry. You do not have enough flour to bake a cake. Sorry. You do not have enough flour to bake a cake.


Output may vary after Testing determineLeftOverCake, because it uses Random as Input.

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