Java-IF'input'='this'{将字符串从数组存储到变量中}

Question

I'm relatively new to programming. I'm trying to make a program at the moment, and I'm trying to figure out how I can do something. I hope you guys can help me as I just don't know how to do this...

So, first of all, I have made an array and filled it with stuff:

String[] pizza = new String[10];
    pizza[0] = "1- Cheese";
    pizza[1] = "2- Wedge";
    pizza[2] = "3- Bacon";
    pizza[3] = "4- Hawaiian";
    pizza[4] = "5- Vegetarian";
    pizza[5] = "6- Pepperoni";
    pizza[6] = "7- Ham";
    pizza[7] = "8- Apple";
    pizza[8] = "9- Grape";
    pizza[9] = "10- Italian";

I want to make it so that I have an IF statement (which is inside a while). I'll just put the code here, and explain after.

int pizzaCounter = 0;

        while(pizzaCounter < 5)
        {

            Scanner pizzaPick = new Scanner(System.in);
            int Pizzas = pizzaPick.nextInt();

            if (Pizzas == 1)
            {
                *Store "1- Cheese" (From pizza[0]) into a variable*

                pizzaCounter++;
            }
            if (Pizzas == 2)
            {
                *Store "2- Wedge" (From pizza[0]) into a variable*

                pizzaCounter++;
            }
            if (Pizzas == 3) etc...

        }

Now at the 'Insert something here' bit, I want to try to make it so that it stores the text from the array(pizza) into some variable which I can print out later... So for example if the user inputs '1' then it takes: "1-Cheese" and stores it in a variable which I can print out later...

Also, I want to make it clean, so that there aren't 10 IF statements prompting each variable thing...?

I don't know if this is even possible, but any help is greatly appreciated! :D

I hope what I am asking here is understandable...

Please, if possible, could you explain what you are doing at each of the steps, so that I can actually understand what is happening, and maybe use the same code later, instead of just copying it and pasting the code? I'm kind of a noob so I think that the more I learn the more I can use later on... Thanks so much! :D

Answer 1

You can replace the entire series of if statements with something like:

string saveName = "";
if ((Pizzas >= 0) && (Pizzas <= 9)) {
    saveName = pizza[Pizzas];           // This is "insert something here".
    pizzaCounter++;
}

// Here, saveName has the pizza name.

---

For a full blown program which allows you to order up to five pizzas, saving the lot and printing them out at the end, see below:

import java.util.Scanner;

public class testprog {
    public static void main (String args[]) {
        String[] pizzaList = {" 0 - End of order",
            " 1 - Cheese", " 2 - Wedge", " 3 - Bacon", " 4 - Hawaiian",
            " 5 - Vegetarian", " 6 - Pepperoni", " 7 - Ham", " 8 - Apple",
            " 9 - Grape", "10 - Italian"};

        int[] orderList = new int[5];  // Ordered pizzas
        int pizzaCount = 0;            //    and count.

        Scanner pizzaPick = new Scanner(System.in);
        while (pizzaCount < 5) {
            // Output the menu.

            System.out.println ("Choose a pizza:");
            for (int i = 0; i < pizzaList.length; i++)
                System.out.println ("   " + pizzaList[i]);

            // Get input, check, and add pizza.

            int thisPizza = pizzaPick.nextInt();
            if (thisPizza == 0) break;

            if ((thisPizza > 0) && (thisPizza < pizzaList.length))
                orderList[pizzaCount++] = thisPizza;

            if ((thisPizza < 0) || (thisPizza >= pizzaList.length))
                System.out.println ("Invalid input of " + thisPizza);
        }

        // Output all pizzas.

        for (int i = 0; i < pizzaCount; i++)
            System.out.println ("Ordered: " + pizzaList[orderList[i]]);
    }
}

Answer 2

String[] PIZZA_LABELS = new String[]{ "1- Cheese", "2- Wedge" ... }
String label;
while(pizzaCounter < 5)
{
        Scanner pizzaPick = new Scanner(System.in);
        int Pizzas = pizzaPick.nextInt();
        label  = PIZZA_LABELS[Pizzas - 1]; // 1-indexed vs 0-indexed
        ...
        System.out.println(label);

'if' is gone. (I would encourage you to look at java.util.Map for a possibly cleaner data structure than the label array).

Answer 3

Don't use capitalized words ( Pizzas ) for local primitives in Java. Conventionally, those are class names.

You want to distinguish between what is the same regardless of the value of Pizzas -- eg, you increment pizzaCounter each time -- and leave that out of the if/elses. If all you need to do is get the name of the type of pizza, then you have a few examples here of how you don't need a set of cases at all, you just need to assign for whatever subsequent use.

If there are some unique things per case, you can use a switch :

http://docs.oracle.com/javase/tutorial/java/nutsandbolts/switch.html

BTW, you can initialize arrays like this:

String eg[] = {
   "one",
   "two",
   "three",
};

Answer 4

There are a few things you can do here to optimize the code. First, drop the while loop in favor of a for loop, like so:

for (int i = 0; i < 5; i++) {
    // Will loop 5 times
}

Second, you could replace the if statements with a switch statement, like so:

switch (pizzaPick.nextInt()) {
    case 0:
        // Do something
        break;
    case 1:
        // Do something else
        break;
    case 2:
        // Etc.
        break
}

However, we can actually optimize this even further, which will drop the need for switch statements at all. First, though, we need a variable to store the picked pizzas. We can use another array, which will be 5 elements long. Create it like so:

String[] pickedPizzas = new String[5];

Now we can do stuff with that to store the picked pizzas. We can then do this in each loop to save the picked pizzas:

pickedPizzas[i] = pizza[pizzaPick.nextInt()];

As you can see, we didn't even need to use ifs or a switch, since we can just use assignment. We can continue the optimization by using bracket syntax for arrays. You can initialize arrays like this:

String[] strArray = {"one", "two", "three", ...};

This saves space and is simpler. To top it off, move the declaration of your scanner outside the loop. Placing it inside the loop will cause it to be re-created and destroyed each time the loop executes, due to the loop's scope. Placing it outside the loop will remedy this.

Here's what the final code might look like:

// Hold all the pizza names
String[] pizzas = {
    "1- Cheese",
    "2- Wedge",
    "3- Bacon",
    "4- Hawaiian",
    "5- Vegetarian",
    "6- Pepperoni",
    "7- Ham",
    "8- Apple",
    "9- Grape",
    "10- Italian"
    };

// Create a variable to hold the selected pizzas
String[] pickedPizzas = new String[5];

// Create Scanner outside loop
Scanner scanner = new Scanner(System.in);

// Loop to get picked pizzas
for (int i = 0; i < 5; i++) {
    // Save picked pizza, subtracting 1 since arrays start at 0
    pickedPizzas[i] = pizzas[scanner.nextInt() - 1];
}

// Do stuff with the users picked pizzas!