Java中动态管理数组元素：从固定数组到ArrayList的实践指南

String[] toppings = {"diced onion", "green pepper", "pepperoni"};

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Scanner;

public class PizzaOrderOptimized {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        System.out.println("---------------------");
        System.out.println("Create Your Own Pizza");
        System.out.println("---------------------");

        // 使用 ArrayList 存储可用配料，实现动态增删
        List<String> availableToppings = new ArrayList<>(Arrays.asList(
                "diced onion", "green pepper", "pepperoni", "sliced mushrooms",
                "jalapenos", "pineapple", "dry red pepper", "basil"
        ));

        // 用于存储用户已选择的配料及其数量
        List<String> selectedToppings = new ArrayList<>();
        List<String> selectedAmounts = new ArrayList<>();

        char userChar = 'y';
        while (userChar == 'y' && !availableToppings.isEmpty()) {
            System.out.println("\nChoose your favorite toppings:");

            // 动态生成菜单，只显示未选择的配料
            for (int i = 0; i < availableToppings.size(); ++i) {
                System.out.println((char) ('A' + i) + ". " + availableToppings.get(i));
            }
            System.out.println("---------------------");

            System.out.print("Enter a choice: ");
            // 注意：为避免Scanner的nextLine()和next()混合使用问题，统一使用nextLine()
            String userChoiceStr = sc.nextLine().trim().toUpperCase();

            if (userChoiceStr.length() == 1) {
                int toppingIndex = userChoiceStr.charAt(0) - 'A';

                if (toppingIndex >= 0 && toppingIndex < availableToppings.size()) {
                    String chosenTopping = availableToppings.get(toppingIndex);
                    System.out.println("You chose: " + chosenTopping);

                    System.out.println("Please choose one amount: ");
                    System.out.println("a. 1/8 cup                 b. 1/4 cup");
                    System.out.print("Enter amount choice: ");
                    String amountChoice = sc.nextLine().trim().toLowerCase();

                    String amount = "";
                    if (amountChoice.equals("a")) {
                        amount = "1/8 cup";
                    } else if (amountChoice.equals("b")) {
                        amount = "1/4 cup";
                    } else {
                        System.out.println("Invalid amount choice. Defaulting to 1/8 cup.");
                        amount = "1/8 cup";
                    }

                    selectedToppings.add(chosenTopping);
                    selectedAmounts.add(amount);

                    // 关键步骤：从可用配料列表中移除已选择的配料
                    availableToppings.remove(toppingIndex);

                    System.out.println("Would you like to add more toppings? Type Y for yes or any other key to submit your recipe.");
                    String continueChoice = sc.nextLine().trim().toLowerCase();
                    userChar = continueChoice.isEmpty() ? 'n' : continueChoice.charAt(0);
                } else {
                    System.out.println("You did not enter a valid topping choice (out of range).");
                }
            } else {
                System.out.println("You did not enter a valid topping choice (invalid format).");
            }
        }

        // 打印最终配方
        System.out.println("\n---------------------");
        System.out.println("Your pizza recipe is:");
        if (selectedToppings.isEmpty()) {
            System.out.println("No toppings selected.");
        } else {
            for (int i = 0; i < selectedToppings.size(); i++) {
                System.out.println(selectedToppings.get(i) + "\t\t" + selectedAmounts.get(i));
            }
        }
        System.out.println("---------------------");

        sc.close();
    }
}

import java.util.Arrays;

public class ArrayManipulation {
    public static String[] removeElementByValue(String[] array, String elementToRemove) {
        // 计算新数组的长度
        int count = 0;
        for (String s : array) {
            if (!s.equals(elementToRemove)) {
                count++;
            }
        }

        String[] newArray = new String[count];
        int newArrayIndex = 0;
        for (String s : array) {
            if (!s.equals(elementToRemove)) {
                newArray[newArrayIndex++] = s;
            }
        }
        return newArray;
    }

    public static void main(String[] args) {
        String[] arr = {"hello", "world", ":)", "world"};
        String[] temp = removeElementByValue(arr, "world");
        System.out.println(Arrays.toString(temp)); // 输出: [hello, :)]
    }
}

import java.util.Arrays;

public class ArrayManipulation {
    public static String[] removeElementByIndex(String[] array, int indexToRemove) {
        if (indexToRemove < 0 || indexToRemove >= array.length) {
            System.out.println("Invalid index for removal.");
            return array; // 返回原数组或抛出异常
        }

        String[] newArray = new String[array.length - 1];
        for (int i = 0, j = 0; i < array.length; i++) {
            if (i == indexToRemove) {
                continue; // 跳过要移除的元素
            }
            newArray[j++] = array[i];
        }
        return newArray;
    }

    public static void main(String[] args) {
        String[] arr = {"hello", "world", ":)"};
        String[] temp = removeElementByIndex(arr, 0);
        System.out.println(Arrays.toString(temp)); // 输出: [world, :)]
    }
}

public class HideElements {
    public static void main(String[] args) {
        String[] myArray = {"apple", "banana", "cherry"};

        // 隐藏 "banana" (假设其索引为1)
        myArray[1] = null;

        System.out.println("Printing array with null elements hidden:");
        for (int i = 0; i < myArray.length; i++) {
            if (myArray[i] != null) {
                System.out.println(myArray[i]);
            }
        }
        // 输出:
        // apple
        // cherry
    }
}