java - 为什么我需要在 BufferedReader 中捕获 close() 异常，但在 PrintWriter 中不需要？

Question

我有一个简单的文件读写功能。

private void WriteToFile(String filename, String val) {
    PrintWriter outStream = null;
    FileOutputStream fos = null;
    try {
        fos = new FileOutputStream(filename);
        outStream = new PrintWriter(new OutputStreamWriter(fos));
        outStream.print(val);
        outStream.close();
    } catch (Exception e) {
        if (outStream != null) {
            outStream.close();
        }
    }
}

private String ReadFile(String filename) {
    String output = "";
    FileReader fr = null;
    BufferedReader br = null;
    try {
        fr = new FileReader(filename);
        br = new BufferedReader(fr);
        output = br.readLine();
        br.close();
    } catch (Exception e) {
        if (br != null) {
            br.close();
        }
    }

    return output;
}

构建时我得到:

unreported exception java.io.IOException; must be caught or declared to be thrown
            br.close();
                    ^

为什么我需要捕获 br.close 但它不会提示 WriteToFile 的 close()？

Answer 1

取自java.io.PrintWriter的源代码:

public void close() {
    try {
        synchronized (lock) {
            if (out == null)
                return;
            out.close();
            out = null;
        }
    }
    catch (IOException x) {
        trouble = true;
    }
}

IOException 被 PrintWriter 中的 close() 方法吞噬

来自java.io.BufferedReader的源代码:

public void close() throws IOException {
    synchronized (lock) {
        if (in == null)
            return;
        in.close();
        in = null;
        cb = null;
    }
}

BufferedReader 抛出 IOException。

这应该可以回答你的问题。