Question

我试图在导入文件后使用try catch语句并在catch下继续获取和错误（FileNOtFoundException e）它告诉我，异常永远不会从try语句体中抛出并将其从正文中删除。

//import scanner needed for input dialog
import java.util.Scanner;  
import java.io.*;
import java.util.InputMismatchException;
import java.text.NumberFormat;


    public class Lab5{
        public static void main(String[]args) throws FileNotFoundException{
            NumberFormat fmtCurr = NumberFormat.getCurrencyInstance();
            Scanner kb = new Scanner(System.in);

        //Get the filename
                String fileName = null;
                File inputFile = new File(fileName);
                Scanner file = new Scanner(inputFile);
                boolean invalid;
            do{
                System.out.print("Data file of prior internet usage: ")
                try{
                    double avg;
                    double paid;
                    double total;
                    System.out.println("Usage history:");
                    while (file.hasNextLine()){
                        avg = file.nextDouble();
                        paid = file.nextDouble();
                        total = file.nextDouble();          
                        System.out.println( "Average Hours Used:" + avg);
                        System.out.println( "Average Paid:" + fmtCurr.format(paid));
                        System.out.println( "Total Paid:" + fmtCurr.format(total));
                    }
                    invalid = false;
                }

            catch(FileNotFoundException e)
                {
                System.out.print("file does not exist");
                invalid = true;
                }
            }

            while(invalid = true);



    }
}

Answer 1

try块必须包含可能引发异常的行，在这种情况下是Scanner file = new Scanner(inputFile);行。如果你在try块中移动该行，那么它将捕获异常（如果它被抛出）。

Answer 2

它告诉我异常永远不会从try语句体中抛出......

是的，它告诉你确切的问题。 java.io.FileNotFoundException块中的任何代码行都不会引发try。

根据您的代码所做的事情，您似乎想要抓住java.util.InputMismatchException。

            catch (InputMismatchException e) // not FileNotFoundException
            {
                System.out.print("Invalid double input");
                invalid = true;
            }

异常处理：尝试使用Java中的catch语句

2 个答案: