Java CharArrayWriter Class

The Java.io.CharArrayWriter class implements a character buffer that can be used as a Writer. Data written to the stream automatically expands the buffer.

Explanation

The CharArrayWriter class is a subclass of the Writer abstract class. Its purpose is to write characters from a char array to a buffer that is also a char array and then from this buffer to a character stream.

Syntax

public class CharArrayWriter extends Writer

Constructor

• CharArrayWriter()
  With the given array of characters, a CharArrayReader is created.
• CharArrayWriter(int initialSize)
  Using the given initial size generates a new CharArrayWriter.

Method

• CharArrayWriter append(char c)
  The specified character is appended to this writer by this method.CharArrayWriter append(CharSequence csq)The given character sequence is appended to this writer by this method.
• CharArrayWriter append(CharSequence csq, int start, int end)
  This method adds a subsequence of the given character sequence to this writer.
• void close()
  This technique ends the stream.
• voidFlush()
  This technique clears the stream.
• void reset()
  This method resets the buffer, allowing you to use it again without wasting the previously allocated buffer.
• Int size()
  This method returns the buffer’s current size.
• char[] toCharArray()
  This method returns a copy of the input data.
• String toString()
  This technique creates a string out of the input data.
• void write(char[] c, int off, int len)
  Writes characters to the buffer using this method.
• void write(int c)
  Write a character to the buffer using this method.
• void write(String str, int off, int len)
  Using this method, a string section is written to the buffer.
• void writeTo(Writer out)
  The contents of the buffer are written to a different character stream using this method.

Field

• protected char[] buf
  This is the buffer used to hold data.
• protected int count
  This is the buffer’s character count.
• protected Object lock
  This is the object that keeps this stream’s operations in sync.

Example

package studytonight;
import java.io.CharArrayWriter;
import java.io.FileWriter;
public class StudyTonight 
{
  public static void main(String args[]) throws Exception
  {
    CharArrayWriter writer=new CharArrayWriter();    
    writer.write("Hello Studytonight");    
    FileWriter fileWriter=new FileWriter("E:\studytonight\\output.txt");   
    writer.writeTo(fileWriter);    
    fileWriter.close();    
    System.out.println("Data is written successfully...");    
  }
}

Output
Data is written successfully…

Example

import java.io.*;
class A
{
public static void main(String... ar)
{
char[] arr1= new char[]{'j','a','v','a'};
char[] arr2= new char[]{'p','r','o','g','r',’a’,’m’};

try
{
CharArrayWriter caw= new CharArrayWriter(); 
System.out.println("Initial Size of the buffer = "+ caw.size());

for(char ch : arr1) 
{
caw.write(ch);
}

caw.write(arr2);  

System.out.println("Content of buffer = "+ caw.toString());
System.out.println("Size of the buffer = "+ caw.size());

FileWriter fw = new FileWriter("D:\\TextBook2.txt");
caw.writeTo(fw);

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

}
}

Output
Initial Size of the buffer = 0
Content of buffer = javaprogram
Size of the buffer = 13

Conclusion

Using the Char array writer class, we can write shared data to several files. This class creates a buffer for writing data. When data is written to the stream, this buffer expands automatically and has no set size.