flush() forces any buffered data to be written to the underlying stream immediately, ensuring data is not lost in the buffer.

The Serializable interface is a marker interface that indicates a class can be serialized. It's found in java.io package and requires no methods to be implemented.

FileReader.read() returns the ASCII/Unicode value of the character as an integer, not the character itself. It returns -1 when EOF is reached.

DataInputStream is specifically designed to read primitive data types (int, float, double, etc.) from a binary stream using methods like readInt(), readFloat(), etc.

FileChannel.transferTo() uses OS-level optimizations for file copying, and NIO channels with direct buffers are most efficient for large file transfers.

SequenceInputStream concatenates multiple input streams, reading from them sequentially as if they were a single stream.

GZIPInputStream decompresses GZIP-compressed data, allowing transparent reading of compressed files as normal streams.

The transient keyword marks fields that should not be serialized, useful for excluding sensitive data or non-serializable objects.

BufferedReader combined with custom parsing logic (using split or regex) handles variable-length fields better than fixed-format alternatives.

Maintaining a constant serialVersionUID and implementing version-aware readObject() methods allows deserializing objects from different class versions.