当我关闭 BufferedInputStream 时，底层 InputStream 是否也关闭了？ [复制]

Question

InputStream in = SomeClass.getInputStream(...);
BufferedInputStream bis = new BufferedInputStream(in);

try {
    // read data from bis
} finally {
    bis.close();
    in.close();    
}

BufferedInputStream.close() 的 javadoc 没有提及底层流是否关闭：

关闭此输入流并释放所有关联的系统资源 与流。一旦流被关闭，进一步读取（）， available()、reset() 或 skip() 调用将引发 IOException。 关闭之前关闭的流没有任何效果。

显式调用in.close() 是必要的，还是应该通过调用bis.close() 来关闭它？

Answer 1

BufferedInputStream 本身不保存任何系统资源；它只是包装了一个保存这些资源的 InputStream。因此 BufferedInputStream 将关闭操作转发到被包装的 InputStream 上，然后它将释放其资源。

Answer 2

来自BufferedInputStream的源码：

public void close() throws IOException {
    byte[] buffer;
    while ( (buffer = buf) != null) {
        if (bufUpdater.compareAndSet(this, buffer, null)) {
            InputStream input = in;
            in = null;
            if (input != null)
                input.close();
            return;
        }
        // Else retry in case a new buf was CASed in fill()
    }
}

所以答案是：是的

Answer 3

这是Java实现

/**
 * Closes this input stream and releases any system resources
 * associated with the stream.
 * Once the stream has been closed, further read(), available(), reset(),
 * or skip() invocations will throw an IOException.
 * Closing a previously closed stream has no effect.
 *
 * @exception  IOException  if an I/O error occurs.
 */
public void close() throws IOException {
    byte[] buffer;
    while ( (buffer = buf) != null) {
        if (bufUpdater.compareAndSet(this, buffer, null)) {
            InputStream input = in;
            in = null;
            if (input != null)
                input.close();
            return;
        }
        // Else retry in case a new buf was CASed in fill()
    }
}

所以，流将被关闭

Answer 4

是的。底层流将被关闭。

Answer 5

当你关闭一个 BufferedInputStream 时，底层的 InputStream 确实也被关闭了。 :)