java 6 IO - 包装流关闭[关闭]

考虑 ：

public static void read(String filename) throws IOException {
    String charsetName = "UTF-8";
    InputStream file = new FileInputStream(filename); // say no problem
    InputStreamReader reader = new InputStreamReader(file, charsetName);
    BufferedReader buffer = new BufferedReader(reader);
    try {
        buffer.readLine();
    } finally {
        try {
            buffer.close();
        } catch (IOException e) {
            // report at least
            e.printStackTrace();
        }
    }
}

If new InputStreamReader(file, charsetName) throws UnsupportedEncodingException, the buffer.close();线路永远不会被调用。另一种方法更加冗长：

InputStream file = new FileInputStream(filename);
try {
    InputStreamReader reader = new InputStreamReader(file);
    try {
        BufferedReader buffer = new BufferedReader(buffer);
        try {
            buffer.readLine();
        } finally {
            buffer.close(); // should catch
        }
    } finally {
        reader.close(); // should catch
    }
} finally {
    file.close(); // should catch
}

它不必要地关闭所有流（同时output.close();应该足够了 - 实际上，如果成功的话，其中任何一个都应该足够 -请参阅 Skeet 代码中的注释 https://stackoverflow.com/questions/326390/how-to-create-a-java-string-from-the-contents-of-a-file#comment23466215_326531).

包装构造函数

BufferedReader buffer = new BufferedReader(
              new InputStreamReader(new FileInputStream(filename), charsetName));

本质上只是隐藏问题。

请注意，我使用了 @TomHawtin-tackline 建议的 try-finally 习惯用法here https://stackoverflow.com/a/3044628/281545例如 - 但更常见的方法：

public static void read(String filename) throws IOException {
    String charsetName = "UTF-8";
    InputStream file = null;
    InputStreamReader reader = null;
    BufferedReader buffer = null;
    try {
        file = new FileInputStream(filename);
        reader = new InputStreamReader(file, charsetName);
        buffer = new BufferedReader(reader);
        buffer.readLine();
    } finally {
        try {
            if(buffer != null) buffer.close();
        } catch (IOException e) {
            // report at least
            e.printStackTrace();
        }
        // Rinse and repeat for the rest
    }
}

一样尴尬。

问题 ：

你会如何处理这个案子？
Would :

public static void read(String filename) throws IOException {
    String charsetName = "UTF-8";
    InputStream file = new FileInputStream(filename);
    try {
        InputStreamReader reader = new InputStreamReader(file, charsetName);
        BufferedReader buffer = new BufferedReader(reader); // Eclipse warning
        buffer.readLine();
        // notice that if these were out put streams we SHOULD FLUSH HERE
    } finally {
        try {
            file.close();
        } catch (IOException e) {
            // report at least
            e.printStackTrace();
        }
    }
}

做 ？换句话说关闭最里面的流（与什么相反usually https://stackoverflow.com/questions/3628899/do-i-need-to-close-inputstream-after-i-close-the-reader asked https://stackoverflow.com/questions/884007/best-way-to-close-nested-streams-in-java）将是最干净的解决方案，当有超过2 https://stackoverflow.com/a/6366543/281545包裹流？是否存在以下情况：finally装饰器也应该关闭()？参见实例点here https://stackoverflow.com/a/884244/281545。请注意 Eclipse 警告：

资源泄漏：“缓冲区”从未关闭

Eclipse 是对的吗？

_{This is Java 6 - Android is Java 6 only I remind you. Trying to factor out IO code in some utility classes, once and for all}

在你最后的方法中，Resource leak根据关闭流的规则，eclipse 显示的警告是正确的。关闭最里面的流只是关闭该流，而不是关闭该流的其他流。但是关闭最外层流是一次性操作，它将自动关闭所有底层流。 正如文章中所指定的始终关闭流 http://www.javapractices.com/topic/TopicAction.do?Id=8 :

如果多个流链接在一起，则关闭其中的一个 是最后建造的，因此处于最高水平 抽象，将自动关闭所有底层流。所以， 只需要在一个流上调用 close 即可关闭（并刷新， 如果适用）整个系列的相关流。

所以我认为以下代码是您案例的解决方案：

public static void read(String filename) throws IOException {
    String charsetName = "UTF-8";
    InputStream file = null;
    InputStreamReader reader = null;
    BufferedReader buffer = null;
    try 
    {
        file = new FileInputStream(filename);                
        reader = new InputStream(file,charsetName);
        buffer = new BufferedReader(reader);
        buffer.readLine();
    } 
    finally 
    {
         closeQuietly(buffer,reader,file);
    }
}

EDIT
正如 @jtahlborn 所建议的，finally 块中编写的代码被包装在实用程序方法中，如下所示：

public static void closeQuietly(Closeable... closeables) 
{ 
    if(closeables == null) 
    { 
        return; 
    } 
    for (Closeable c : closeables) 
    { 
        doCloseQuietly(c); 
    } 
} 
public static void doCloseQuietly(Closeable c)
{
    try
    {
        if (c != null)
        {
            c.close();
        }
    }
    catch (IOException ex)
    {
        ex.printStackTrace();
    }
}