I/O Fundamentals in JAVA 4

I/O Stream Chaining:-

• A program rarely uses a single stream. Instead, it chains a series of streams together to process the data.
• The given below demonstrates an example input stream; in this case, a file stream is buffered for efficiency and then converted into data (Java primitives) items.

This is an input stream chain example

Data Source è FileInputStream => BufferedInputStream => DataInputStream è Program

• And given below demonstrates an example output stream; in this case, data is written, then buffered, and finally written to a file.

This is an input stream chain example

Program è DataOutputStream => BufferedOutputStream => FileOutputStream è Data Sink

 

Processing Streams:-

• A processing stream performs some sort of conversion on another stream. Processing Streams are also called as filter streams.
• The filter input stream is created with the connection to an existing input stream.
• This is done so that when you try to read from the filter input stream object, it supplies you with characters that originally came from the other stream object.
• This enables you to convert the raw data into a more usable form for your application.
• The given below lists the built in processing streams that are included in a java.io package.

 

Type                              Character Streams                 Byte Streams

Buffering                        BufferedReader                       BufferedInputStream

                                           BufferedWriter                        BufferedOuputStream

Filtering                         FilterReader                                FilterInputStream

                                           FilterWriter                                 FilterOuputStream

Converting between       InputStreamReader

bytes and characters      OutputStreamWriter

*Performing object                                                         ObjectInputStream

Serialization                                                                       ObjectOutputStream

Performing                                                                          DataInputStream

Data Conversion                                                                DataOutputStream

Counting                         LineNumberReader              LineNumberInputStream

Peeking ahead              PushbackReader                    PushbackInputStream

Printing                           PrintWriter                                 PrintStream

Note: – The FilterXYZ streams are abstract classes and cannot be used directly. You can subclass them to implement your own processing streams.

• It is easy to create new processing streams.

Basic Byte Stream Classes:-

The FileInputStream class and FileOutputStream Class:-

• The FileInputStream class and FileOutputStream Class are node stream classes and, as the name suggests, they use disk files.
• The constructor for these classes enables you to specify the path of the file to which they are connected.
• To construct the FileInputStream, the associated file must be exist and be readable. If you construct a FileOutputStream, the output file is overwritten if it already exists.

FileInputStream infile = new FileInputStream(“myfiles11.dat”);

FileOutputStream infile = new FileOutputStream(“myfiles12.dat”);

The BufferedInputStream class and BufferedOutputStream Class:-

• Use a BufferedInputStream class and BufferedOutputStream class filter streams to increase the efficiency of I/O operations.

The PipeInputStream class and PipeOutputStream Class:-

• We use piped streams for communicating between threads. A PipedInputStream object in one thread receives its input from a complementary PipedOutputStream object in another thread.
• The piped streams must have both an input side and an output side to be useful.

The DataInputStream class and DataOutputStream Class:-

• The DataInputStream class and DataOutputStream class are called filter streams enables reading and writing of java primitive types and some special formats using streams.
• The following methods are provided for the different primitives,

The methods of DataInputStream class:-

The methods of DataInputStream class are as follows:

• byte readByte()
• long readLong()
• double readDouble()

The methods of DataOutputStream class:-

The methods of DataOutputStream class are as follows:

• void writeByte(byte)
• void writeLong(long)
• void writeDouble(double)

• The methods of DataInputStream are paired with the methods of DataOutputStream.

• These streams have methods for reading and writing strings but do not use these methods.
• They have been deprecated and replaced by readers and writers.

The ObjectInputStream class and ObjectOutputStream Class:-

• The ObjectInputStream class and ObjectOutputStream class enable reading from and writing Java Objects to streams.
• Writing an object to a stream primarily involves writing the values of all the fields of the object.
• If the fields are objects themselves, these objects should also be written to the stream.

Note: – If the fields are declared as transient or static, their values are not written to the stream.

• Reading an object from the stream involves, reading the object type creating the blank object of that type and filling it with that data that was written.
• A Persistent storage of an object can be accomplished if files (or other persistent storage) are used as the stream.
• The Java API provides a standard mechanism that completely automates the process of writing and reading objects from streams.

Note: – If the stream is a network socket stream, the objects are sterilized before sending and desterilized after receiving on another host or process.

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