根据键盘输入返回值？

Question

如果用户键入"C",我只想输出为12.0,输入"H"就相同.问题是输入存储为字符串正确吗？我试图通过Double.parseDouble将字符串转换为double

---

import java.util.Scanner;

public class Elements {

    Scanner input=new Scanner(System.in);   
    public static final double H = 1.0; 
    public static final double Li = 6.9;
    public static final double Be = 9;
    public static final double B = 10.8;
    public static final double C = 12.0;

    public double output() {
        return C ; // I want the user to choose the variable to return
    }
}

Answer 1

您不希望将值存储为字段,而是将它们存储在地图中:

private static final Map<String, Double> values = new HashMap<String, Double>();
static {
    values.put("H", 1.0);
    values.put("Li", 6.9);
    // and so on...
}

然后,在output()中:

return values.get(input.nextLine());

使用常量字段进行此操作的唯一方法是使用反射,并且您真的不想去那里.