我在try / finally中关闭了文件,但代码分析警告我：

• Possible failure to close a FileOutputStream
• Possible failure to close a PrintWriter
• Possible failure to close an OutputStreamWriter

怎么会发生失败？如何确保FileStream已关闭？

public void writeFile(String filepath)
{
    BufferedWriter bw = null;
    PrintWriter pw = null;
    try {
        File file = new File(filepath);
        bfw = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(file), "UTF-8"));
        pw = new PrintWriter(bfw);

     //do something

    }catch(Exception e){
        e.printStackTrace();
    }
    finally{
        try{
            bfw.close();
            pw.close();
        }catch(Exception e){
            e.printStackTrace();
        }
    }
}

解决方法:

How can failure happen?

看看你的finally块：

finally{
    try{
        bfw.close();   <== exception occured here
        pw.close();    <== this is not execute
    }catch(Exception e){
        e.printStackTrace();
    }
}

如果bfw.close()中发生异常怎么办？ pw.close()永远不会执行.这导致资源泄漏.

How can I ensure the FileStream is closed?

有人已经指出最后使用try / catch / finally.
但如果你不喜欢看到这么多尝试捕获,我建议你使用像Apache Commons IO这样的库.

解：

try {

   ........
} finally {
    IOUtils.closeQuietly(bfw);
    IOUtils.closeQuietly(pw);
}

是的,如果使用Java 7或更高版本,您总是拥有try-with-resources.