中断后程序仍在循环 Java

Question

我一直在开发一个程序，该程序将接受用户在周期性 table 中输入元素的名称或符号，然后输出有关该元素的一些信息。在这里问了很多问题之后，我已经知道程序正确地存储了所有数据，以我想要的方式输出它并且可以接受名称或符号的输入。我现在遇到的问题是我插入到循环中的中断实际上并没有从循环中中断，我真的不确定为什么。该程序将继续请求输入，即使它收到了正确的输入。此外，如果用户输入的是符号而不是名称，程序会在最终正确输出之前反复告诉用户他们的输入无效（然后重新启动循环而不是中断循环）。我是 Java 的新手，所以如果有人可以帮助我解决这些问题中的任何一个并解释问题发生的原因以及他们如何相当简单地解决问题，我将不胜感激。

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) {

        System.out.println("Enter the name or symbol of an element in the periodic table. ");
        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;
                } 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;
                    } catch(IllegalArgumentException e) {
                        System.out.println("That name or symbol is not valid. Please try again. ");
                        continue;
                    }
                }
            }
        } while (true);
    }
}

Answer 1

问题是 break 在 for 循环中，所以它只会中断 for 循环。如果你想打破 do-while 循环，你可以使用标签：

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) {
                    System.out.println("That name or symbol is not valid. Please try again. ");
                    continue;
              }
          }
     }
} while (true);

中断后程序仍在循环 Java

Program still looping after break in Java

java

validation

enums

loops

break