Question

import java.util.ArrayList;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.FileReader;
import java.util.ArrayList;
import java.util.Random;

public class WordList {
    private static Random r = new Random();

    private static ArrayList<String> words = new ArrayList<String>();
    String filename = "Cities.txt";

    public static void main(String[] args) throws IOException {
        WordList wl = new WordList();
        buffR(wl.filename);
        System.out.println(words);
        System.out.println(getRandomWord());
    }

    public static ArrayList buffR(String filename) throws IOException {
        words.clear();
        String line = null;
        BufferedReader br = null;

        br = new BufferedReader(new FileReader(filename));
        while ((line = br.readLine()) != null) {
            words.add(line);
        }
        br.close();
        return words;
    }

    public static String getRandomWord() {
        WordList wl = new WordList();
        String randomWord;
        if (words.size() > 0) {
            int index = r.nextInt(words.size());
            randomWord = words.get(index);
        } else {
            randomWord = wl.filename + " is missing";
        }
        return randomWord;
    }
}

当我运行此代码时，我有一个java.io.FileNotFoundException（关于我的BufferedReader方法）（我故意放了一个没有现成的文件）。但是，我已经在我的方法头中抛出了IOException。我该怎么办才能再次遇到这个错误？

Answer 1

添加throws的所有内容都表示该方法可以抛出Exception，如果抛出它，您希望处理Exception。要做到这一点，你可以包装代码块是一个try-catch块。如果它应该被抛出，则无法阻止Exception被抛出，但是try-catch块会使它不会崩溃。 Oracle Tutorial非常有帮助。

对于此示例，您可以执行以下操作：

try 
{
  //This already throws FileNotFoundException
  br = new BufferedReader(new FileReader(filename));
} 
catch(FileNotFoundException e)
{
  e.printStackTrace();
}

Answer 2

这种做法怎么样？我改变了一些事情，但我在下面记录了它。

// static, pass in the initial words lits.
public static List<String> buffR(List<String> words,
    String filename) throws IOException {
  words.clear(); // If you want to reuse it.
  String line = null;
  BufferedReader br = null;
  File file = null; // A file to read.

  try {
    file = new File(filename); // Create a File object.
    if (! file.exists()) { // It's not there!
      throw new FileNotFoundException("Could not find file: " + filename);
    }
    // Proceed as before...
    br = new BufferedReader(new FileReader(file));
    while ((line = br.readLine()) != null) {
      words.add(line);
    }
  } finally {
    br.close(); // Let's try to not leak any resources.
  }
  return words;
}

使用BufferedReader时如何抛出FileNotFoundException？

2 个答案: