java - FileInputStream读取方法的风格

Question

FileInputStream 读取方法具有签名(这是正确的术语吗？) -

     public int read(byte[] b) throws IOException

     // Reads up to b.length bytes of data from this input stream into an array of bytes. This method blocks until some input is available.
     // Returns: the total number of bytes read into the buffer, or -1 if there is no more data because the end of the file has been reached.

拥有这样的签名比这样的签名有什么优势 -

     public byte[] read(int numberOfBytes) throws IOException
     // Reads up to numberOfBytes bytes of data from this input stream into an array of bytes.
     // Returns- an array of bytes read. Array is empty if there is no more data because the end of the file has been reached.

Answer 1

第一种形式允许您在多次执行中重复使用相同的byte[] 数组。基本上，您可以读取产生最少垃圾(低 GC Activity )的整个流。

后者显然更方便，但每次在 read() 方法内部执行时都需要创建 byte[] 的新实例。这意味着在读取 10 GiB 文件(即使是 100 字节 block )时，您的应用程序将总共分配 10 GiB 内存 - 不是同时分配，但垃圾收集器仍然会疯狂工作。

看看Collection.toArray(T[]) - 它遵循相同的原则。