Question

我想写一个程序Pizza.java，该程序使用户最多可以输入15个比萨的浇头，然后按字母顺序打印出浇头。另外，浇头应该用数字列出。

示例输出将是这样

我写的代码如下：

import java.util.*;
 public class Pizza {
 public static final int numbers=15;

  public static void main(String[] args) {


  Scanner input = new Scanner(System.in);

  String []toppings;
  System.out.println("Enter a toping (or type quit): ");

  String a= input.nextLine();

 // how do I add String a to the array toppings?   
  int count=1;
  while (!a.equals("quit")&&count<numbers){
     System.out.println("Enter a topping (or type quit): ");
     a= input.nextLine();
     if(!a.equals("quit"))
        // how do I add String a to the array toppings?     
     count++;


  }
    if(count==numbers)
     System.out.println("No more toppings allowed.");
     int i=1;
     Arrays.sort(toppings); //sorts the array in alphabetical order
    while (int i<=count){
  System.out.println(i+". "+Arrays.toString(toppings));      
  }

     if(a.equals("quit")){
      Arrays.sort(toppings); //sorts the array in alphabetical order

      while (int j<=count){
      System.out.println(j+". "+Arrays.toString(toppings));      
       }
  }






        }



         }

如何完成此代码？任何帮助将不胜感激

Answer 1

您可以使用列表而不是数组来使其更简单：

import java.util.*;

public class Pizza {
    public static final int numbers = 15;

    public static void main(String[] args) {
        List<String> toppings = new ArrayList<>();
        Scanner input = new Scanner(System.in);

        int attempt;
        for (attempt = 0; attempt < numbers; attempt++) {
            System.out.print("Enter topping topping (or type quit): ");
            String topping = input.nextLine();

            if (topping.equals("quit")) {
                break;
            }

            toppings.add(topping);
        }

        if (attempt == numbers) {
            System.out.println("No more toppings allowed.");
        }

        Collections.sort(toppings);

        for (int position = 0; position < toppings.size(); position++) {
            System.out.println((position + 1) + ". " + element);
        }
    }
}

或使用数组：

import java.util.*;

public class Pizza {
    public static final int numbers = 15;

    public static void main(String[] args) {
        String[] toppings = new String[numbers];
        Scanner input = new Scanner(System.in);

        int attempt;
        for (attempt = 0; attempt < numbers; attempt++) {
            System.out.print("Enter topping topping (or type quit): ");
            String topping = input.nextLine();

            if (topping.equals("quit")) {
                break;
            }

            toppings[attempt] = topping;
        }

        if (attempt == numbers - 1) {
            System.out.println("No more toppings allowed.");
        } else {
            // Remove "null" elements from "toppings" array
            String[] temp = new String[attempt];

            for (int position = 0; position < attempt; position++) {
                temp[position] = toppings[position];
            }

            toppings = temp;
        }

        Arrays.sort(toppings);

        for (int position = 0; position < toppings.length; position++) {
            String element = toppings[position];

            System.out.println((position + 1) + ". " + element);
        }
    }
}

Answer 2

如您所说，不允许使用ArrayList。这是我使用String数组的方法。对您来说最有趣的部分应该是Arrays.copyOfRange方法，您也可以用System.arraycopy(...)调用来代替。

import java.util.*;

public class Pizza {
    private static final int MAX_TOPINGS = 15;
    private final String QUIT_KEYWORD = "quit";

    public static void main(String[] args) {
        new Pizza().printToppings(MAX_TOPINGS);
    }

    public void printToppings(int maxTopings){
        Scanner input = new Scanner(System.in);
        String[] toppings = new String[maxTopings];

        int count;
        for (count = 0; count < maxTopings; count++) {
            System.out.printf("Enter topping topping (or type %s): ", QUIT_KEYWORD);
            String topping = input.nextLine();
            if (topping.toLowerCase().equals(QUIT_KEYWORD)) {
                break;
            }
            toppings[count] = topping;
        }

        if (count+1 == maxTopings) {
            System.out.println("No more toppings allowed.");
        } else {
            toppings = Arrays.copyOfRange(toppings, 0, count);
        }

        Arrays.sort(toppings);

        for (int i = 0; i < count; i++) {
            System.out.println(i+1 + ". " + toppings[i]);
        }
    }
}

对于以下输入：

Enter topping topping (or type quit): Cheese
Enter topping topping (or type quit): Onions
Enter topping topping (or type quit): Tuna
Enter topping topping (or type quit): quit

您将收到以下输出：

1. Cheese
2. Onions
3. Tuna

Answer 3

不要打扰while循环。如果要处理数组，则应使用for循环。

就将字符串添加到数组而言，在尝试使用它们之前，您确实应该learn about arrays。在使用它之前，您甚至都没有初始化数组。

当用户输入“ quit”时，可以使用break语句退出循环。

import java.util.Arrays;
import java.util.Scanner;

public class Pizza {
    //If actually want the user to be able to enter 15 toppings, then set numbers to 16.
    public static final int numbers = 16;

    public static void main(String[] args) {

        @SuppressWarnings("resource")
        Scanner input = new Scanner(System.in);

        //Initialize the array
        String[] toppings = new String[numbers];

        int count;
        //Use a for loop
        for (count = 0; count < numbers; count++) {
            System.out.println("Enter a toping (or type quit):");
            toppings[count] = input.nextLine();
            if (toppings[count].equalsIgnoreCase("quit")) {
                //If they enter quit, break from the loop
                break;
            }
        }

        if (count == numbers)
            System.out.println("No more toppings allowed.");

        //If they do not fill all 15 indices of the array, trim out the empty indices.
        if (count < numbers)
            toppings = Arrays.copyOfRange(toppings, 0, count);
        Arrays.sort(toppings);

        //Use another for to print them
        for (int i = 0; i < count; i++) {
            System.out.println(i + ". " + toppings[i]);
        }

    }

}

比萨披萨配料

3 个答案: