Question

import java.util.*;


public class Inheritance {

    public static Scanner objScan = new Scanner(System.in);

    public static void main(String[] args) {

        System.out.println("Enter name:");
        String strName = objScan.nextLine();

        double dSalary;
        int iYears;
        String strTIN;
        String strLoopControl = "1";

        try {
            System.out.println("Enter salary:");
            dSalary = dGetSalary();
            System.out.println("Enter years worked:");
            iYears = iGetYears();
            System.out.println("Enter ID number:");
            strTIN = strGetID();  

            Employee1 objEmp = new Employee1(strName, dSalary, iYears, strTIN);
            objEmp.print();
        }

        catch (Exception e) {           
            if (e instanceof NegativeInputException) {
                strLoopControl = "0";
                System.out.println(e.getMessage());
                //strLoopControl = "0";
            }
            else if (e instanceof ZeroIdentificationException) {
                System.out.println(e.getMessage());
            }

        }

    }

   public static double dGetSalary () throws NegativeInputException {
       double dSalary;

      do { 
       try {    
           dSalary = objScan.nextDouble();

           if (dSalary < 0) {
               throw new NegativeInputException();
           }
           return dSalary;
       }

       catch (NegativeInputException nie) {
           throw nie;
       } 
      } while (dSalary<0);
   } 

    public static int iGetYears() throws NegativeInputException {
        int iYears;

        try {
            iYears = objScan.nextInt();

            if (iYears < 0) {
                throw new NegativeInputException();
            }
            return iYears;
        }

        catch (NegativeInputException nie) {
        throw nie;
       }

    }

    public static String strGetID() throws ZeroIdentificationException {
        String strTIN; 

        try {
            strTIN = objScan.next();

            if (strTIN.equals("0000000")) {
                throw new ZeroIdentificationException();
            }
            return strTIN;
        }

        catch (ZeroIdentificationException zie) {
            throw zie;
        }
}

}

class NegativeInputException extends Exception {

    public NegativeInputException() {
        super("You have inputted a negative number.");
    }

    public NegativeInputException (String strMessage) {
        super(strMessage);
    }
}

class ZeroIdentificationException extends Exception {
    public ZeroIdentificationException() {
        super("You inputted an invalid ID number. \n Please input again.");

    }

    public ZeroIdentificationException(String strMessage) {
        super(strMessage);
    }
}

class Person1 {

    private String strName;

    public Person1() {
        strName = "";
      }

    public Person1(String strName) {
        this.strName = strName;
    }

    public void setName(String strName) {
        this.strName = strName;
    }

    public String getName() {
        return strName;
    }

    public void print() {
        System.out.println("Name: " +strName);
    }
}

class Employee1 extends Person1 {

    private String strName;
    private double dSalary;
    private int iYears; 
    private String strTIN;

    public Employee1 (String strName, double dSalary, int iYears, String strTIN) {

        this.strName = strName;
        this.dSalary = dSalary;
        this.iYears = iYears;
        this.strTIN = strTIN;

    }

    public void print() {
        System.out.println();
        System.out.print("Name: " +this.strName);
        System.out.println();
        System.out.print("Salary:" +this.dSalary);
        System.out.println();
        System.out.print("Years WorkedS:" +this.iYears);
        System.out.println();
        System.out.print("ID Number:"  +this.strTIN);
    }

        }

这是一个要求员工记录的程序。它要求提供姓名，工资，工作年限和身份证号码。每当用户输入负值时捕获异常，并在strTIN变量中输入“0000000”时捕获异常。这个程序完美无缺，但是每当输入负值和“0000000”时我需要重新输入。我尝试过使用do-while语句，但没有运气。谁能帮我？我有一个使用“flag”来控制循环的想法但我不知道在我的代码中把它放在哪里。我很确定有一种方法可以重新输入，我只是想不出来。

Answer 1

你的方法被打破 - 他们试图在值为负时循环，但是如果它是否定的话它们会抛出异常......所以他们只会经历一次循环，要么返回一个值，要么抛出异常。

你想要这样的东西：

public static double getNonNegativeDouble(Scanner scanner) {
  while (true) {
    double value = scanner.nextDouble();
    if (value >= 0) {
      return value;
    }
  }
}

你应该可能重复提示并在无效输入上给出错误信息，但是......

另请注意：

抓住一个例外只是为了再次抛出它是可怕的：

// Ick: just don't catch! (May mean you don't need "try" block at all.)
catch (NegativeInputException nie) {
    throw nie;
}

您的“伪匈牙利语”方法名称违反了Java命名约定
抓取Exception然后使用instanceof检查不同类型是可怕的;只是抓住你感兴趣的类型。

Answer 2

您可以将NegativeInputException代码包装在仅返回正值的while循环中，而不是抛出nextInt ...

此外，将输入功能包装在

等方法中也许是个好主意

int readInteger(int minValue, int maxValue) {
    if (minValue >= maxValue)
       throw new IllegalArgumentException("...")
    while(true) {
       System.out.println("Please enter an integer ("+minValue+"-"+maxValue+")");
       int val = objScan.nextInt();
       if (val >= minValue && val <= maxValue) return val;
    }
}
double readDouble(...

每当用户输入负数时，我都需要帮助尝试重新输入值

2 个答案: