java - 在针对枚举 Java 中的每个项目检查输入后如何跳出循环？

Question

我正在尝试制作一个程序，允许用户输入元素周期表中元素的名称或符号，然后输出有关该元素的一些数据。到目前为止，我已经设法让用户能够输入名称或符号并正确输出，但是如果用户输入错误，则代码不会输出任何内容，并且将停止接受以下输入一个符号，并且只接受名称的输入。我想知道如何能够跳出循环并告诉用户，只有在针对枚举中的每个项目检查输入后，他们的输入才无效，因为我当前的解决方案不起作用。我是 Java 新手，因此非常感谢有关如何以及为何的简单解释。

import java.util.Scanner;
public class PeriodicTable {

    public enum Element {
        Hydrogen("H", "Nonmetal", "1.008"),
        Helium("He", "Noble Gas", "4.003"),
        Lithium("Li", "Alkali Metal", "6.941"),
        Beryllium("Be", "Alkaline Earth", "9.012"),
        Boron("B", "Semimetal", "10.811"),
        Carbon("C", "Nonmetal", "12.011"),
        //The rest of the periodic table is here, I just removed it for the sake of this post.

        private String symbol;
        private String group;
        private String weight;

        private Element(String symbol, String group, String weight) {
            this.symbol = symbol;
            this.group = group;
            this.weight = weight;
        }
    }

    static Element cName = null;
    public static void main(String[] args) {

        int counter = 0;
        System.out.println("Enter the name or symbol of an element in the periodic table. ");
        outer:
        do {
            Scanner reader = new Scanner(System.in);
            String input = reader.nextLine().trim();
            for (Element sy : Element.values()) {
                if (sy.symbol.equalsIgnoreCase(input)) {
                    System.out.println("Element: " + sy + " (" + sy.symbol + ")" + "\nGroup: " + sy.group + "\nAtomic Mass: " + sy.weight);
                    reader.close();
                    break outer;
                } else {
                    try {
                        cName = Element.valueOf(input.substring(0, 1).toUpperCase() + input.substring(1).toLowerCase());
                        System.out.println("Element: " + cName + " (" + cName.symbol + ")" + "\nGroup: " + cName.group + "\nAtomic Mass: " + cName.weight);
                        reader.close();
                        break outer;
                    } catch(IllegalArgumentException e) {
                        if(counter > Element.values().length) {
                            System.out.println("That name or symbol is not valid. Please try again. ");
                            continue outer;
                        } else {
                            counter++;
                            continue;
                        }
                    }
                }
            }
        } while (true);
    }
}

Answer 1

我会避免在循环中使用valueOf方法。相反，您可以迭代元素并为每个元素检查其名称(使用 name 方法)及其符号。

Scanner reader = new Scanner(System.in);
outer: while (true) {
    System.out.println("Enter the name or symbol of an element in the periodic table. ");
    String input = reader.nextLine().trim();
    for (Element sy : Element.values()) {
        if (sy.symbol.equalsIgnoreCase(input) || sy.name().equalsIgnoreCase(input)) {
            System.out.println("Element: " + sy + " (" + sy.symbol + ")" + "\nGroup: " + sy.group + "\nAtomic Mass: " + sy.weight);
            break outer;
        }
    }
    System.out.println("No such element found. ");
}
reader.close(); // this might be a bad idea

我还会避免关闭reader，因为这也会关闭System.in，并且您将无法读取更多输入。