java - 在 Java 中，关闭父输入流是否也会关闭其子输入流？

Question

FileInputStream fis = new FileInputStream(gzipFile);
GZIPInputStream gis = new GZIPInputStream(fis);
gis.close();
fis.close();

fis.close() 是必要的吗？虽然我正在运行这段代码，但似乎没有出现任何错误。

Answer 1

您应该看到 GZIPInputStream.close() 的实现。

/**
 * Closes this input stream and releases any system resources associated
 * with the stream.
 * @exception IOException if an I/O error has occurred
 */
public void close() throws IOException {
    if (!closed) {
        super.close();  
        eos = true;
        closed = true;
    }
}

如果您看一下 GZIPInputStream 的构造函数，它看起来像这样:

/**
 * Creates a new input stream with the specified buffer size.
 * @param in the input stream
 * @param size the input buffer size
 * @exception IOException if an I/O error has occurred
 * @exception IllegalArgumentException if size is <= 0
 */
public GZIPInputStream(InputStream in, int size) throws IOException {
super(in, new Inflater(true), size);
    usesDefaultInflater = true;
        readHeader(in);
}

观察变量in。请注意它是如何传递给父类(super class)的，在本例中为 InflaterInputStream。

现在，如果我们看一下 InflaterInputStream.close() 方法的实现，我们会发现:

/**
 * Closes this input stream and releases any system resources associated
 * with the stream.
 * @exception IOException if an I/O error has occurred
 */
public void close() throws IOException {
    if (!closed) {
        if (usesDefaultInflater)
            inf.end();
    in.close();
        closed = true;
    }
}

很明显，正在调用 in.close()。因此，包装(装饰)FileInputStream 也会在调用 GZIPInputStream.close() 时关闭。这使得调用 fis.close() 变得多余。