Question

My lecturer gave us a simple assignment of reading from a text file(as a database) and computing allowances based on age and gender. When I read a line from the txt file, I read each word and stored in a string. But it is a bit confusing for me, what if i have a line in my file say-

bucky roberts M 23

now i have firstname = bucky; lastname = roberts; sex = M and age = 23.

Now, based on the above fields if i make a computation, it works fine.

But what if my lecturer says rewrite the same line to be - bucky M 23 firstname = bucky lastname = M sex = 23 and age = null

Thats how the program reads the line from the file. Now, if i make a if-else statement based on age, i will get an error of java.util.MismatchException. How do i resolve this issue and at the same time find a way such that even if my lecturer tempers with the database, the program runs fine. Here is a part of the code below:-

AdultMale.java class:-

public class AdultMale extends Male {

    public void getAllowance() {
        readfromFile();
        while(in.hasNext())
        {
            firstname = in.next();
            lastname = in.next();
            gender = in.next();
            age = in.nextInt();

            if(gender.equals("M") || gender.equals("Male") || gender.equals("male") ||gender.equals("m"))
            {
                AdultAllowance();

            }

         }
        in.close();

    }       
}

Male.java class:-

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;

 public class Male extends Members{


        Scanner in;
        public void getAllowance() {

        }

        public void readfromFile()
        {
            try {
                in = new Scanner(new File("Dbase.txt"));
            } catch (FileNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }


        public void AdultAllowance()
        {
            if(age>=18)
            {
                total = 500;
                total = total + 1000;
                System.out.println(firstname + "\t" +lastname+"\t"+ age + "\t"+ gender+"\t"+total);
                total = 0;
            }

        }

        public void MinorAllowance()
        {
            if(age <18)
            {
                total = 500;
                total = total + 200;
                System.out.println(firstname + "\t"+lastname+"\t" + age + "\t"+ gender+"\t"+total);
                total = 0;
            }
        }
    }

Members class:-

public abstract class Members {
            String firstname,lastname,gender;
            int age;
            double total ; 
        }

My txt database is called - "Dbase.txt" which contains the following:-

Sam     Bell        M   17
Becky   roberts     F   23
Bucky   taylor      M   21
Sammy   lyson       F   16
Terry   gibson      F   23

Answer 1

阅读整行，然后使用它。所以，这样的东西应该工作（未经测试的代码，用textpad编写）。这将处理所有情况。

while(scanner.hasNextLine()) {
String line = scanner.nextLine();
String[] arr = line.split("\\s+");
 for(String str : arr) {
  if(str.equalsIgnoreCase("M") || str.equalsIgnoreCase("Male")); // check for gender for each line in file.
    gender = "M";
    }
  else if(str.matches("\\d+")) { // check for age.
    age = Integer.parseInt(str);
    }
  else if(firstName!=null || !firstName.isEmpty()) // for string that is not age or gender.
   {
    firstName = str;
   }
  else{
      lastname = str;
     }
}
}

How do i solve the java.util.MismatchException in Java?

1 个答案: