OutputStreamWriter

OutputStreamWriter class is a subclass of Writer abstract class. Using OutputStreamWriter class, we can convert a character, character arrays or a String to bytes before it is written to an output stream. Hence, OutputStreamWriter class acts as a converter of characters to bytes.

Constructor :

OutputStreamWriter(OutputStream is)
This constructor creates an OutputStreamWriter object wrapped around an OutputStream to write data to this OutputStream in the form of bytes. Example-: `char arr[] ={'a', 'b', 'c', 'd'}; FileOutputStream fos = new FileOutputStream("D://TextBook.txt"); OutputStreamWriter osr = new OutputStreamWriter (fos);`

In this example, FileOutputStream is wrapped inside OutputStreamWriter. We can only write bytes through FileOutputStream, hence, OutputStreamWriter class will first convert the characters in a character array, arr, to bytes before writing them to a file TextBook.txt using FileOutputStream.

Point to remember

FileOutputStream is a subclass of OutputStream

Methods for writing using OutputStreamWriter

Some methods that we generally use while working with CharArrayWriter are shown in the table below :

Methods	Description
flush()	This method flushes any data to be written out of this character output stream.
write(int c)	This method writes one character at a time to this character output stream's buffer.
write(char[])	This method writes a whole character array at a time to this character output's buffer.
write(String str)	This method writes a String to this character output stream's buffer.
close()	This method closes this output stream and also frees any resources connected with this output stream.

Writing a character array and a String to a file using OutputStreamWriter.

We are writing to a file called TextBook.txt using its path D:\\TextBook.txt.

// Program to write a character array and a String using OutputStreamWriter.

import java.io.*;

class A
{
public static void main(String... ar)
{

String str="Hello World";
char[] arr= {'a', 'b', 'c' , 'd' , 'e'};

try
{
FileOutputStream fos= new FileOutputStream("D:\\TextBook.txt"); 
OutputStreamWriter osw= new OutputStreamWriter(fos); 

// writing each character of character array using for-each loop
for(char c : arr)
{
osw.write(c);   
}

//writing a String
osw.write(str); 

osw.flush();
osw.close();
}
catch(IOException e)
{
System.out.println(e);
}
}
}

Output is -:

After the execution of this program, a file TextBook.txt is created in the D: drive, with contents -:
abcdeHello World

Program Analysis

OutputStream i.e. FileOutputStream is wrapped inside OutputStreamWriter.
FileOutputStream writes data only in terms of bytes, hence, OutputStreamWriter class will first internally convert the characters in a character array, arr, to bytes before writing them to a file TextBook.txt using FileOutputStream.
OutputStreamWriter's write() methods write a character/character array or String to FileOutputStream.
Finally all the open streams are closed by caling close() method.

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