Java：未报告的异常java.io.FileNotFoundException；必须抓取或声明抛出[副本]

Question

import java.io.File;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {

        Scanner sc = new Scanner(new File("C:\\Users\\User\\Selenium\\scrapjv\\interface\\NASDAQlist.txt"));
        List<String> symbolList = new ArrayList<String>();
        while (sc.hasNextLine()) {
            symbolList.add(sc.nextLine());
        }

        PrintWriter logput = new PrintWriter("C:\\Users\\User\\Selenium\\scrapjv\\interface\\log.txt", "UTF-8");
        for (String symb : symbolList) {
            System.out.println(symb);
        }
        logput.close();
    }
}

Answer 1

如果找不到文件，您正在调用的某些方法可以抛出FileNotFoundException:

 public Scanner(File source) throws FileNotFoundException
 public PrintWriter(String fileName) throws FileNotFoundException

Java的编译器检查一些抛出的异常（RuntimeException及其子类以外的异常）是否被捕获或声明抛出。否则编译将失败。这有助于在程序运行之前，在编译时发现一些错误。

一种选择是声明调用函数以抛出异常或超类：

 public static void main(String[] args) throws FileNotFoundException {

    File inFile = new File("C:\\Users\\User\\Selenium\\scrapjv\\interface\\NASDAQlist.txt");
    try {
        Scanner sc = new Scanner( inFile );
        List<String> symbolList = new ArrayList<String>();
        while (sc.hasNextLine()) {
            symbolList.add(sc.nextLine());
        }
    }
    catch ( FileNotFoundException e ) {
        System.out.println("Could not find file: " + inFile.getAbsolutePath());
    }