Overview
- Input/Output Streams
- Byte Oriented Streams
- Character Oriented Streams
- Object Serialization
- Channel Based I/O
Input/Output Streams
- Stream is an abstraction and can be thought of as flow of data from source to sink.
- Source or InputStream initiates the flow of data.
- Sink or OutputStream terminates the flow of data.
- There is no concept of index like array in stream. It is just the flow of data.
- Two types of Streams: Byte & Character Based
- System.in is an InputStream representing standard input (usually the keyboard).
- System.out is a PrintStream representing standard output (usually the console).
- System.err is also a PrintStream representing standard error output.
Byte Oriented Stream
- InputStream class is used for reading the data in terms of bytes.
- Some of the methods are read(), read(byte[]), read(byte[],int,int), close() etc.
- OutputStream class is used for representing the output stream of data.
- Some of the methods are write(int), write(byte[]), write(byte[], int,int), close() etc.
- Demo
Character Oriented Stream
- Reader and Writer classes & their sub-classes are used for dealing with the characters.
- read() and print() methods are used by these to read and write respectively.
- BufferedReader and BufferedWriter classes provide the built-in buffer for reading and writing the data.
- readLine() and write() are some methods used for reading and writing data by these classes.
- Demo
Serializing Objects
- Serialization of objects is needed in case one wants to persist the objects in the permanent storage.
- For reading & writing an object in a file, it should implement the Serializable interface.
- ObjectInputStream & ObjectOutputStream are used to read & write the objects to a file.
- They make use of witeObject & readObject methods, along with readXXX & writeXXX methods for the primitives.
File I/O
- Java provides classes like File, FileInputStream, FileOutputStream, FileReader, and FileWriter for file I/O operations.
- To read from a file:
try (FileInputStream fis = new FileInputStream
("file.txt")) {
int data;
while ((data = fis.read()) != -1) {
// Process data
}
} catch (IOException e) {
e.printStackTrace();
}
Channel Based I/O
- Java Channels are similar to the Streams, with few differences:-
- We can both read and write to a channel.
- These are always read from/written to a buffer.
- These can be read and written asynchronously.
- Buffers are block of memory closely coupled with the underlying operating system.These too like arrays are of fixed capacity.
- Data can be read/written into a buffer and these are used when interacting with channels.
- Demo
