Java OutputStreamWriter

OutputStreamWriter is a class in java.io class that is useful for the conversion of character stream into a byte stream. This conversion of characters into bytes is done using charset encoding that has been specified. It contains a write () method that calls the encoding converter to convert a character into a stream of bytes from where the resultant bytes are sent into the buffer where it is accumulated and sent to the outputstream. The characters are passed to the write () method without being buffered, thus leading to frequent converter invocation, thus being used with BufferedWriter.

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Syntax:

public class OutputStreamWriter extends Writer

This syntax depicts that this is a public class that means it can be instantiated from anywhere in the project. This class is a direct subclass of an abstract class- Writer class that deals with writing to the character streams.

How OutputStreamWriter works in Java?

• OutputStreamWriter class is a direct subclass of the Writer class that helps to write to the output stream. This class converts each character of character stream to a byte stream, thus acting as a bridge between the character stream and byte stream.
• For this conversion, it uses the specified charset of the encoder, such as UTF-8, etc., passed as arguments to its write method. Since the characters being passed to the write method is not buffered, the output byte stream is then buffered before writing to the output stream.
• To optimize the performance of the application as well as to avoid frequent converter invocation, it is recommended to use it with BufferedWriter.

Constructors

To create an instance of OutputStreamWriter class, we have the following 4 types of constructors:

1. OutputStreamWriter (OutputStream out)

This constructor returns an instance of OutputStreamWriter with default character encoding. This is the simplest way to create an instance.

Example:

FileOutputStream fileObj = new FileOutputStream (String path); //

This is an instance of OutputStream.

OutputStreamWriter output = new OutputStreamWriter (fileObj);//

The above instance is passed as an argument to specify the file where the output needs to be written.

2. OutputStreamWriter (OutputStream out, CharsetcsObj)

This constructor returns an instance of OutputStreamWriter that uses the Charset specified. Here charset specified can be like Charset.forName ( “UTF8”), creating an instance of charset as an argument to the method.

Example:

OutputStreamWriter output = new OutputStreamWriter (fileObj,Charset.forName ( "UTF8"));

3. OutputStreamWriter (OutputStream out, CharsetEncoder enc)

This constructor returns an instance of OutputStreamWriter that uses the specified Charset encoder.

Example:

CharsetEncoderencoder = B2CConverter.UTF_8.newEncoder ()
OutputStreamWriter output = new OutputStreamWriter (fileObj, encoder);

4. OutputStreamWriter (OutputStream out, StringcsName)

This constructor returns an instance of OutputStreamWriter that uses the specified Charset name.

Example:

OutputStreamWriter output = new OutputStreamWriter (fileObj,"UTF-8");

Here, the charset Name used for converting a character stream to the byte stream is “UTF-8”.

Methods

1. close ():- This method helps to close the stream after flushing it. No Parameter is required, and nothing is returned from this method.

Syntax 

public void close ()

2. flush ():- This method helps to flush the stream.No Parameter is required, and nothing is returned from this method.

Syntax 

public void flush ()

3. getEncoding ():- This method helps to retrieve the name of charset encoding being used by the given instance of OutputStreamWriter. No parameter needs to be passed while calling the method.

Syntax

public String getEncoding ()

The string representation of the name of the Encoding being used by the instance is returned.

4. write (char[] charbuf, int off, int len):- This method helps to write a particular portion of an array of characters that starts from the offset position and whose length is ‘len’.This method throwsIOException in case any input is given is incorrect or null.

Syntax

public void write (char[] charbuf, int off, int len)

This method just writes the converted byte stream to the output file. It does not return anything.

5. write (int ch):- This method is used to write a single character to the stream specifying its ASCII character. This method throwsIOException in case any input is given is incorrect or null.

Syntax

public void write (int ch)

This method just writes the converted byte stream to the output file. It does not return anything.

6. write(String str, int off, int len):- This method is used to write a portion of a string starting with the given offset and given length to the stream.

Syntax

public void write (String strObj, int offset, int lgth)

This method just writes the converted byte stream to the output file. It does not return anything.

Examples

Below the examples of Java OutputStreamWriter:

Example 1

import java.io.*;
public class StreamDemo
{
public static void main (String[] args)
{
String data = "LetsLearnOuptputStreamClass";
try
{
OutputStream file = new FileOutputStream ("abc.txt");
OutputStreamWriter outObj = new OutputStreamWriter (file);
FileInputStream inFileObj = new FileInputStream ("abc.txt");
outObj.write (data, 5, 6);
outObj.flush ();
System.out.println ( "Name of Encoding used here is : " + outObj.getEncoding ());
for (int i = 0; i<6; i++)
{
System.out.println ( "Character written is : " + (char) inFileObj.read());
}
outObj.close ();
}
catch (Exception ex)
{
System.out.println ( "Error Occurred");
ex.printStackTrace ();
}
}
}

Output:

Example 2

import java.io.*;
public class StreamDemo
{
public static void main (String[] args)
{
try
{
OutputStream g = new FileOutputStream ( "C:/Users/savij/Desktop/abc.txt");
OutputStreamWriter outObj = new OutputStreamWriter (g);
FileInputStream in = new FileInputStream ( "C:/Users/savij/Desktop/abc.txt");
outObj.write (69);
outObj.write (68);
outObj.write (85);
outObj.write (67);
outObj.write (66);
outObj.write (65);
outObj.flush ();
for (int i = 0; i< 6; i++)
{
System.out.println ( "The char being written: " + (char) in.read());
}
outObj.close ();
}
catch (Exception ex)
{
System.out.println ( "Error");
ex.printStackTrace ();
}
}
}

Output:

Example 3

//package Proc;
import java.io.*;
public class StreamDemo
{
public static void main (String[] args)
{
char[] data = {'E','D','U','C','B','A'};
try
{
OutputStream file = new FileOutputStream ( "abc.txt");
OutputStreamWriter outObj = new OutputStreamWriter (file);
FileInputStream inFileObj = new FileInputStream ( "abc.txt");
outObj.write (data,2, 4);
outObj.flush ();
for (int i = 0; i<4; i++)
{
System.out.println ( "Character written is : " + (char) inFileObj.read());
}
outObj.close ();
}
catch (Exception ex)
{
System.out.println ( "Error Occurred");
ex.printStackTrace ();
}
}
}

Output:

Conclusion – Java OutputStreamWriter

OutputStreamWriter is a utility that acts as a bridge from the character stream to a byte stream. It contains a write method that takes input in the form of characters and converts them into bytes using the specified charset or charset encoder for e.g., UTF-8. This class’s efficiency and performance can be enhanced if BufferredWriter is being used instead of Writer to write the resultant byte stream to the output streams.

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