以编程方式确定IOException的原因？

import java.io.*;

public class IOExceptionExample {
    public static void main(String[] args) {
        File file = new File("non_existent_file.txt");
        try {
            FileReader fileReader = new FileReader(file);
            BufferedReader bufferedReader = new BufferedReader(fileReader);
            String line;
            while ((line = bufferedReader.readLine()) != null) {
                System.out.println(line);
            }
            bufferedReader.close();
        } catch (FileNotFoundException e) {
            System.out.println("FileNotFoundException: " + e.getMessage());
        } catch (IOException e) {
            System.out.println("IOException: " + e.getMessage());
        }
    }
}