Java I/O

Java I/O is built on a small set of abstract concepts that underlie every I/O operation in the language: streams, readers, writers, channels, and buffers.

Byte streams are the fundamental I/O abstraction in Java for reading and writing raw binary data.

Character streams, represented by the Reader and Writer abstract base classes, handle text data by abstracting away the encoding and decoding between Java's internal…

File handling in Java spans two generations of API: the legacy java.io.File class introduced in Java 1.0, and the modern java.nio.file package (NIO.2) introduced in Java…

The java.io.File class is Java's original file system abstraction, present since Java 1.0.

FileInputStream is a concrete InputStream subclass that reads raw bytes from a file on the file system.

FileOutputStream is a concrete OutputStream subclass that writes raw bytes to a file on the file system.

Buffered streams wrap an underlying unbuffered stream with an in-memory buffer, dramatically reducing the number of native I/O system calls by batching reads and writes.

FileReader is a convenience class for reading character files, extending InputStreamReader with a FileInputStream underneath.

FileWriter is a convenience class for writing characters to a file, extending OutputStreamWriter with a FileOutputStream underneath.

BufferedReader wraps any Reader with an in-memory character buffer, dramatically reducing system calls for character-by-character or line-by-line reading.

BufferedWriter wraps any Writer with an in-memory character buffer, reducing system calls by accumulating characters until the buffer fills, flush() is called, or…

PrintWriter is a character-based output class that wraps any Writer or OutputStream and adds convenience methods for printing formatted representations of all Java…

DataInputStream wraps any InputStream and adds methods for reading Java primitive types in a machine-independent binary format.

DataOutputStream wraps any OutputStream and adds methods for writing Java primitive types in a machine-independent binary format using big-endian byte order.

Java serialization is the mechanism for converting an object graph into a sequence of bytes that can be stored to a file, transmitted over a network, or persisted in a…

Deserialization is the process of reconstructing a Java object from a byte stream previously produced by serialization.

The transient keyword marks an instance field as excluded from Java's default serialization mechanism.

Externalization is Java's mechanism for giving a class complete, explicit control over its serialized form.