Question

我是Java编程的新手。我开发了一个Pizza类，它接受参数并输出描述和成本。我开发了一个PizzaOrderArray类，它将比萨订单存储在一个数组中。我有一个包含main方法的类。

当我尝试打印订单的值时，没有任何打印，但调试显示输入了正确的方法和循环。

我做错了什么？我投入了很多时间，我仍然很困惑。有什么建议吗？谢谢！我很感激。

Pizza.java

import java.text.NumberFormat;
import java.util.Locale;

public class Pizza {

    public Pizza(String size, int numCheeseTop, int numPepTop, int numHamTop) {
        if (!setPizzaSize(size)) {
            System.out.println(size + " is invalid size." + "Use small, medium or large.");
        }
        setNumCheese(numCheeseTop);
        setNumPep(numPepTop);
        setNumHam(numHamTop);
    }

    public Pizza(String size, int numPepTop, int numHamTop) {
        if (!setPizzaSize(size)) {
            System.out.println(size + " is invalid size." + "Use small, medium or large.");
        }
        pizza_cheese = 0;
        setNumPep(numPepTop);
        setNumHam(numHamTop);
    }

    public Pizza(String size, int numHamTop) {
        if (!setPizzaSize(size)) {
            System.out.println(size + " is invalid size." + "Use small, medium or large.");
        }
        pizza_pep = 0;
        setNumHam(numHamTop);
        pizza_cheese = 0;
    }

    public Pizza(String size) {
        if (!setPizzaSize(size)) {
            System.out.println(size + " is invalid size." + "Use small, medium or large.");
        }
        pizza_cheese = 0;
        pizza_pep = 0;
        pizza_ham = 0;
    }

    public Pizza() {
        pizza_size = "small";
        pizza_cheese = 0;
        pizza_pep = 0;
        pizza_ham = 0;
    }

    public Pizza(Pizza copyPizza) {
        pizza_size = copyPizza.getPizzaSize();
        pizza_cheese = copyPizza.getNumCheese();
        pizza_pep = copyPizza.getNumPep();
        pizza_ham = copyPizza.getNumHam();
    }

    //Setters
    public boolean setPizzaSize(String size) {
        if (size.equalsIgnoreCase("small") || (size.equalsIgnoreCase("medium") || (size.equalsIgnoreCase("large")))) {
            pizza_size = size.toLowerCase();
            return true;
        }
        return false;
    }

    public void setNumCheese(int numCheeseTop) {
        pizza_cheese = numCheeseTop;
    }

    public void setNumPep(int numPepTop) {
        pizza_pep = numPepTop;
    }

    public void setNumHam(int numHamTop) {
        pizza_ham = numHamTop;
    }
    //End of setters

    //Getters
    public String getPizzaSize() {
        return pizza_size;
    }

    public int getNumCheese() {
        return pizza_cheese;
    }

    public int getNumPep() {
        return pizza_pep;
    }

    public int getNumHam() {
        return pizza_ham;
    }

    //End of getters
    public double calcCost() {
        if (pizza_size.toLowerCase() == "small") {
            return 10 + ((pizza_cheese + pizza_pep + pizza_ham) * 2);
        }
        if (pizza_size.toLowerCase() == "medium") {
            return 12 + ((pizza_cheese + pizza_pep + pizza_ham) * 2);
        }
        if (pizza_size.toLowerCase() == "large") {
            return 14 + ((pizza_cheese + pizza_pep + pizza_ham) * 2);
        }
        if (pizza_size.toLowerCase() != "small" && pizza_size.toLowerCase() != "medium"
                && pizza_size.toLowerCase() != "large") {
            System.out.println("Invalid pizza size");
            return 0;
        }
        return 0;
    }

    public String getDescription() {
        return pizza_size + " pizza with " + pizza_cheese + " cheese toppings " + pizza_pep + " pepperoni toppings and "
                + pizza_ham + " ham toppings ";  //+ " which is " + money.format(pizza2.calcCost());
    }

    //private String pizza_size;
    //private int pizza_cheese, pizza_pep, pizza_ham;  
    public String pizza_size;
    public int pizza_cheese, pizza_pep, pizza_ham;

} //End of Pizza class

PizzaOrderArray.java

import static java.lang.System.out;

public class PizzaOrderArray {

    public String pizza_size;
    public int pizza_cheese, pizza_pep, pizza_ham;

    //private String pizza_size;
    //private int pizza_cheese; pizza_pep; pizza_ham;
    private Pizza[] pizza;
    private int index = 0;

    public PizzaOrderArray() {
        System.out.println("PizzaOrderArray()");
        index = 1;
        pizza = new Pizza[index];
    }

    public PizzaOrderArray(int i) {
        System.out.println("PizzaOrderArray(int i)");
        index = 1;
        pizza = new Pizza[index];
    }

    public PizzaOrderArray(PizzaOrderArray poa) {
        System.out.println("PizzaOrderArray(PizzaOrderArray poa)");
        pizza = new Pizza[poa.index];
        index = poa.index;
        for (int i = 0; i < poa.index; i++) {
            System.out.println("PizzaOrderArray(PizzaOrderArray poa) for loop");
            pizza[i] = new Pizza(poa.pizza[i]);
        }
    }

    public void setPizza(int index1, Pizza newpizza) {
        System.out.println("Inside of setPizza");
        pizza[index1] = new Pizza(newpizza);
    }

    public String getPizzaSize() {
        System.out.println("Inside of getPizzaSize");
        return pizza_size;
    }

    public int getNumCheese() {
        System.out.println("Inside of getNumCheese");
        return pizza_cheese;
    }

    public int getNumPep() {
        System.out.println("Inside of getNumPep");
        return pizza_pep;
    }

    public int getNumHam() {
        System.out.println("Inside of getNumHam");
        return pizza_ham;
    }

    public String toString() {
        String s = "";
        int indexUsed = 0;
        System.out.println("Inside of toString");
        for (int i = 0; i < indexUsed; i++) {
            s = (s + pizza[i].toString());
        }
        System.out.println("Inside of toString for loop");

        return s;
    }

    public double calcTotal() {
        double r = 0.0;
        System.out.println("Inside of calcTotal");

        for (int i = 0; i < index; i++) {
            System.out.println("Inside of calcTotal for loop");
            r = r + pizza[i].calcCost();
        }
        return r;
    }

    public boolean equals(PizzaOrderArray orderarray) {
        boolean r = false;
        System.out.println("Inside of equals");
        if (orderarray.pizza.length != pizza.length) {
            System.out.println("Inside of equals if");
            return r;
        }

        for (int i = 0; i < orderarray.pizza.length; i++) {
            if (pizza[i].equals(orderarray.pizza[i])) {
                System.out.println("Inside of equals for-if");
                r = true;
            } else {
                System.out.println("Inside of equals for-else");
                return false;
            }
        }
        System.out.println("Return of equals");
        return r;
    }

} //End of PizzaOrderArray class

V4_Project_15_page_418.java

import java.text.DecimalFormat;
import java.util.Scanner;
import java.util.Arrays;

public class V4_Project_15_page_418 {

    public static void main(String args[]) {
        //Order1
        PizzaOrderArray order1 = new PizzaOrderArray();
        Pizza pizzaone = new Pizza("Medium", 0, 0, 0);
        Pizza pizzatwo = new Pizza("Small", 1, 0, 0);
        order1.setPizza(0, pizzaone);
        System.out.println("Order 1: ");
        System.out.println(order1.toString());
        System.out.println(order1);
        System.out.println();

        //Order2
        Pizza pizzathree = new Pizza(pizzatwo);
        PizzaOrderArray order2 = new PizzaOrderArray(2);
        order2.setPizza(0, pizzaone);
        order2.setPizza(0, pizzatwo);
        System.out.println("Order 2: ");
        System.out.println(order2.toString());
        System.out.println(order2);
        System.out.println();

        //Order3
        PizzaOrderArray order3 = new PizzaOrderArray(1);
        order3.setPizza(0, pizzaone);
        order3.setPizza(0, pizzatwo);
        System.out.println("Order 3: ");
        System.out.println(order3.toString());
        System.out.println(order3);
        System.out.println();

        //Order4
        PizzaOrderArray order4 = new PizzaOrderArray(order3);
        System.out.println("Order 4: ");
        System.out.println(order4.toString());
        System.out.println(order4);
        //TEST THE PROGRAM
        System.out.println("TEST:  The total for order 4 is: " + order4.calcTotal());
        System.out.println();

        //Order5
        PizzaOrderArray order5 = new PizzaOrderArray(order1);
        System.out.println("Order5: ");
        System.out.println(order5);
        System.out.println();

    }//End of main class

}//End of V4_Project_15_page_418 class

输出：

PizzaOrderArray()
Inside of setPizza
Order 1:
Inside of toString
Inside of toString for loop

Inside of toString
Inside of toString for loop


PizzaOrderArray(int i)
Inside of setPizza
Inside of setPizza
Order 2:
Inside of toString
Inside of toString for loop

Inside of toString
Inside of toString for loop


PizzaOrderArray(int i)
Inside of setPizza
Inside of setPizza
Order 3:
Inside of toString
Inside of toString for loop

Inside of toString
Inside of toString for loop


PizzaOrderArray(PizzaOrderArray poa)
PizzaOrderArray(PizzaOrderArray poa) for loop
Order 4:
Inside of toString
Inside of toString for loop

Inside of toString
Inside of toString for loop

Inside of calcTotal
Inside of calcTotal for loop
Invalid pizza size
TEST:  The total for order 4 is: 0.0

PizzaOrderArray(PizzaOrderArray poa)
PizzaOrderArray(PizzaOrderArray poa) for loop
Order5:
Inside of toString
Inside of toString for loop

Answer 1

仔细查看这个for循环中的条件，它不会打印任何东西，因为条件永远不会为真，因为i永远不会小于indexUsed {{1} }}

Answer 2

还需要注意：

for(int i = 0; i < indexUsed; i++) 
    s= (s + pizza[i].toString());
    System.out.println("Inside of toString for loop");

表示：

for(int i = 0; i < indexUsed; i++) {
    s= (s + pizza[i].toString());
}
    System.out.println("Inside of toString for loop");

所以这是System.out.println误导你，你永远不会＆＃34;在＆＃34; for循环。

我认为总是使用大括号＆＃39; {}＆＃39; with for / while循环。

Answer 3

摘录

int indexUsed = 0; System.out.println("Inside of toString"); for(int i = 0; i < indexUsed; i++) s= (s + pizza[i].toString());错误，因为indexUsed为0

，所以for循环永远不会被执行

Answer 4

在你的toString方法中，for循环条件永远不会变为真（在第一次迭代之前，0＆lt; 0变为false＆amp;循环终止而不执行一次）所以循环永远不会执行。

您可以尝试将for循环语句更改为：

 for(int i = 0; i < index; i++)

toString（）的Java值不打印

4 个答案: