I/O Streams in Java (Input/Output stream) .

 

Input/Output Stream

Java IO (Input and Output) is a process of reading data from a source and writing text data to a destination(file).

Stream : 

Stream in Java represents sequential flow (or unbroken flow) of data from one place to another place.

- Java uses the concept of a stream to make I/O operations fast.

- The java.io package contains all the classes required for input and output operations. We can perform file handling in Java by Java I/O API.

Types of Stream in Java

1.Input stream 

2.Output stream  

1.Input stream : 

1. An InputStream is used to read data from a source, such as a file, network socket, or an array.
2. It is an abstract class. 
3. Some inbuild subclasses for read data as from source follow

- FileInputStream : for reading data from a file .

- ByteArrayInputStream : for reading data from a byte array. 

- SocketInputStream : for reading data from a network socket.

2.Output Stream:

1. An OutputStream is used to write data to a destination, such as a file, network socket, or an array. 
2. It is also an abstract class, and you use its subclasses to handle specific data destinations. 
3. Some commonly used subclasses for write data to destination as follow

- FileOutputStream : for writing data to a file , 

- ByteArrayOutputStream : for writing data to a byte array

- SocketOutputStream : for writing data to a network socket.

Stream Classes in Java

Java's I/O streams are categorized into two types: 

1.byte streams class  (support for handling I/O operations based on bytes)

2.character streams class (support for managing I/O operations on characters)

(Note : 1 byte = 8 bit so byte = units of 8-bits data  & character = 16-bit Unicode characters) 

1.Byte streams class 

• Byte streams in Java are designed to provide a convenient way for handling the input and output of bytes (i.e., units of 8-bits data). 
• We use them for reading or writing to binary data I/O.
• Byte streams are especially used when we are working with binary files(Only Machine readable) file such as executable files, image files, and files in low-level file formats such as .zip, .class, .obj, and .exe.

There are two kinds of byte stream classes in Java. They are as follows:

1.InputStream classes

2.OutputStream classes

1.InputStream: 

• This abstract class serves as the base class for all byte input stream classes. 
• It provides methods like read() and read(byte[] buffer) to read bytes from a source.

2.OutputStream: 

• This abstract class is the base class for all byte output stream classes. 
• It provides methods like write(int b) and write(byte[] buffer) to write bytes to a destination.

-Examples of byte stream classes:

FileInputStream: Reads data from a file as a sequence of bytes.

FileOutputStream: Writes data to a file as a sequence of bytes.

ByteArrayInputStream: Reads data from an in-memory byte array.

ByteArrayOutputStream: Writes data to an in-memory byte array.

2.Character Stream Class

•  Character streams in Java are designed for handling the input and output of characters. They use 16-bit Unicode characters.
• character stream classes are mainly used to read characters from the source and write them to the destination.
• Character streams are more efficient than byte streams. They are mainly used for reading or writing to character or text-based I/O such as text files, text documents, XML, and HTML files.

( Note: Unicode is a 2-byte, 16-bit character set having 65,536 (i.e. 2^16) different possible characters. Only about 40,000 characters are used in practice, the rest are reserved for future purposes. )

Types of CharacterStream class.

Character stream classes also contain two kinds of classes. They are as follow:

1. Reader Stream classes

2. Writer Stream classes

1.Reader Stream: 

• The abstract base class for all character input stream classes.
• It provides methods like read() and read(char[] buffer) to read characters from a source.
• It is Similar like Input Stream class The only difference is that Input Stream uses bytes, whereas Reader Stream classes use characters.

2.Writer Stream: 

• The abstract base class for all character output stream classes. 
• It provides methods like write(int c) and write(char[] buffer) to write characters to a destination.
• Writer stream classes are similar to output stream classes with only one difference that output stream classes use bytes to write while writer stream classes use characters to write.
• In fact, both output stream and writer stream classes use the same methods.

Examples of character stream classes:

FileReader: Reads data from a file as a sequence of characters.

FileWriter: Writes data to a file as a sequence of characters.

StringReader: Reads data from a String object.

StringWriter: Writes data to a String object.

BufferedReader: read characters from the buffered input character stream.

InputStreamReader: This class is used to translate (or convert) bytes to characters.

PipeReader: read characters from the connected piped output.

PushBackReader: This class allows one or more characters to be returned to the input stream.