需要添加无参数构造函数。困惑什么也

Question

我现在需要添加一个无参数构造函数，我有我的课程和一个驱动程序。我假设我将构造函数与其他人一起放入类中，但不知道如何去做。我需要没有参数的构造函数默认2勺香草与所有标准浇头。 这里是我到目前为止有：

import java.util.Scanner; 
public class Sundae 
{ 
    public static final double TAX = 0.08625; 
    private String icecream; 
    private int scoops; 
    private double scoopCost; 
    private String toppings; 
    private String allChoices; 
    private String deluxeToppings; 
    private int counter = 0; 
    private double costOfDeluxeToppings = 0; 
    private double costOfSundae = 0; 
    Scanner input = new Scanner(System.in); 
    public String iceCreamFlavor() 
    { 
     System.out.println("1. vanilla | 2. peanut butter | 3. chocolate " 
       + "| 4. mint chocolate chip |\n 5. coffee | 6. strawberry | 7. raspberry " 
       + "| 8. knickerbocker glory | 9. cookies and creme"); 
     int flavor = input.nextInt(); 
     switch(flavor) 
     { 
     case 1: 
      icecream = "vanilla"; 
      break; 
     case 2: 
      icecream = "peanut butter"; 
      break; 
     case 3: 
      icecream = "chocolate"; 
      break; 
     case 4: 
      icecream = "mint chocolate chip"; 
      break; 
     case 5: 
      icecream = "coffe"; 
      break; 
     case 6: 
      icecream = "strawberry"; 
      break; 
     case 7: 
      icecream = "raspberry"; 
      break; 
     case 8: 
      icecream = "knickerbocker glory"; 
      break; 
     case 9: 
      icecream = "cookies and cream"; 
      break; 
     default: 
      icecream = "vanilla"; 
     } 
     return icecream; 
    } 

    public int numberOfScoops() 
    { 
     scoops = input.nextInt(); 
     switch(scoops) 
     { 
     case 1: 
      scoops = 1; 
      break; 
     case 2: 
      scoops = 2; 
      break; 
     case 3: 
      scoops = 3; 
      break; 
     case 4: 
      scoops = 4; 
      break; 
     case 5: 
      scoops = 5; 
      break; 
     case 6: 
      scoops = 6; 
      break; 
     default: 
      scoops = 2; 
     } 
     return scoops; 
    } 

    public double costForScoops() 
    { 
     switch(scoops) 
     { 
     case 1: 
      System.out.println("1 scoop cost $1.79"); 
      scoopCost = 1.79; 
      break; 

     case 2: 
      System.out.println("2 scoops cost $2.79"); 
      scoopCost = 2.79; 
      break; 

     case 3: 
      System.out.println("3 scoops cost $3.79"); 
      scoopCost = 3.79; 
      break; 

     case 4: 
      System.out.println("4 scoops cost $4.79"); 
      scoopCost = 4.79; 
      break; 

     case 5: 
      System.out.println("5 scoops cost $5.79"); 
      scoopCost = 5.79; 
      break; 

     case 6: 
      System.out.println("6 scoops cost $6.79"); 
      scoopCost = 6.79; 
      break; 

     default: 
      System.out.println("2 scoops cost $2.79"); 
      scoopCost = 2.79; 
      break; 
     } 
     return scoopCost; 
    } 

    public String standardToppingList() 
    { 
     System.out.println("1. whipped cream | 2. syrup | 3. chocolate sprinkes " 
       + "| 4. rainbow sprinkes | 5. cherry"); 
     String choice1 = ""; 
     String choice2 = ""; 
     String choice3 = ""; 
     String choice4 = ""; 
     String choice5 = ""; 

     int choice = 0; 
     while(choice != -1) 
     { 
      choice = input.nextInt(); 
      switch(choice) 
      { 
      case 1: 
       choice1 = "whipped cream, "; 
       System.out.println(choice1); 
       break; 

      case 2: 
       choice2 = "syrup, "; 
       System.out.println(choice2); 
       break; 

      case 3: 
       choice3 = "choclate sprinkles, "; 
       System.out.println(choice3); 
       break; 

      case 4: 
       choice4 = "rainbow sprinkles, "; 
       System.out.println(choice4); 
       break; 

      case 5: 
       choice5 = "cherry, "; 
       System.out.println(choice5); 
       break; 

      case -1: 
       break; 

      default: 
       choice = -1; 
       choice1 = "whipped cream, "; 
       choice2 = "syrup, "; 
       choice3 = "choclate sprinkles, "; 
       choice4 = "rainbow sprinkles, "; 
       choice5 = "cherry, "; 
       break; 
      } 
     } 
     toppings = choice1 + choice2 + choice3 + choice4 + choice5; 
     System.out.println("Your choices of toppings are: " + toppings); 
     return toppings; 
    } 

    public String freeSyrupChoice() 
    { 
     System.out.println("1. hot fudge | 2. chocolate | 3. caramel | 4. strawberry"); 
     int choice = 0; 
     String choice1 = ""; 
     String choice2 = ""; 
     String choice3 = ""; 
     String choice4 = ""; 
     while(choice != -1) 
     { 
      choice = input.nextInt(); 
      switch(choice) 
      { 
      case 1: 
       choice1 = "hot fudge, "; 
       System.out.println(choice1); 
       break; 

      case 2: 
       choice2 = "chocolate, "; 
       System.out.println(choice2); 
       break; 

      case 3: 
       choice3 = "caramel, "; 
       System.out.println(choice3); 
       break; 

      case 4: 
       choice4 = "strawberry, "; 
       System.out.println(choice4); 
       break; 

      case -1: 
       break; 

      default: 
       choice = -1; 
       choice1 = "hot fudge, "; 
       break; 
      } 
     } 
     allChoices = choice1 + choice2 + choice3 + choice4; 
     System.out.println("Your choices of syrup include " + allChoices); 
     return allChoices; 
    } 

    public String deluxeToppingList() 
    { 
     System.out.println("1. M&Ms | 2. Crushed Oreos | 3. Reeses | 4. Brownie Crunchies" 
       + " | 5. Brownie Crunchies | 6. Kit Kats \n| 7. Marshmallow | 8. Granola clusters" 
       + " | 9. Peanuts | 10. Walnuts"); 
     String choice1 = ""; 
     String choice2 = ""; 
     String choice3 = ""; 
     String choice4 = ""; 
     String choice5 = ""; 
     String choice6 = ""; 
     String choice7 = ""; 
     String choice8 = ""; 
     int choice = 0; 
     while(choice != -1) 
     { 
      choice = input.nextInt(); 
      switch(choice) 
      { 
      case 1: 
       choice1 = "M&M's, "; 
       System.out.println(choice1); 
       counter++; 
       break; 

      case 2: 
       choice2 = "Crushed Oreos, "; 
       System.out.println(choice2); 
       counter++; 
       break; 



      case 3: 
       choice3 = "Reeses, "; 
       System.out.println(choice3); 
       counter++; 
       break; 

      case 4: 
       choice4 = "Brownie Crunchies, "; 
       System.out.println(choice4); 
       counter++; 
       break; 

      case 5: 
       choice5 = "Kit Kats, "; 
       System.out.println(choice5); 
       counter++; 
       break; 

      case 6: 
       choice6 = "Granola Clusters, "; 
       System.out.println(choice6); 
       counter++; 
       break; 

      case 7: 
       choice7 = "Peanuts, "; 
       System.out.println(choice7); 
       counter++; 
       break; 

      case 8: 
       choice8 = "Walnuts, "; 
       System.out.println(choice8); 
       counter++; 
       break; 
      case -1: 
       break; 

      default: 
       choice = -1; 
       break; 

      } 
     } 
     deluxeToppings = choice1 + choice2 + choice3 + choice4 + choice5 + choice6 + choice7 + choice8; 
     System.out.println("Your choices of deluxe toppings are: " + deluxeToppings); 
     return deluxeToppings; 
    } 

    public int counterD() 
    { 
     System.out.println("You got " + counter + " deluxe toppings"); 
     return counter; 
    } 

    public double costOfDeluxeToppings() 
    { 
     costOfDeluxeToppings = counter * 1.25; 
     System.out.printf("%s%.2f%s" , "Each deluxe topping cost $1.25 each ", 
     costOfDeluxeToppings, " will be added to your total."); 
     return costOfDeluxeToppings; 
    } 

    public double costOfSundae() 
    { 
     costOfSundae = scoopCost + costOfDeluxeToppings; 
     return costOfSundae; 
    } 

    public void outputOrder() 
    { 
     System.out.println("Your order consists of " + scoops + " scoop/s of " + icecream + 
       " icecream with " + toppings + allChoices + deluxeToppings); 
     System.out.printf("%s%.2f\n" , "Your sub-total is: $" , costOfSundae); 
     double tax = costOfSundae * TAX; 
     System.out.println("+ 8.625%"); 
     double total = costOfSundae + tax; 
     System.out.printf("%s%.2f" , "Your total is: $" , total); 

    } 
} 

Answer 1

我需要无参数的构造函数默认为2勺香草与所有标准的浇头。

public Sundae() { 
    this.icecream = "vanilla" ; 
    this.scoops = 2; 
    this.toppings = "list, of, all, standard, toppings" ; 
} 

我想指出的是，你可能可以减少你的成员变量的数量。

例如

public double costOfSundae() 
{ 
    costOfSundae = scoopCost + costOfDeluxeToppings; 
    return costOfSundae; 
} 

可以简单地

public double costOfSundae() 
{ 
    return scoopCost + costOfDeluxeToppings; 
}