Java.io.CharArrayWriter class in Java | Set 1

java.io.CharArrayWriter class creates a character buffer that can be used as a writer. The buffer automatically grows when data is written to the stream. The data can be retrieved using toCharArray() and toString(). 
Declaration: 

public class CharArrayWriter
   extends Writer

Constructor : 

• CharArrayWriter() : Creating a CharArrayWriter from a specified character array.
• CharArrayWriter(int size) : Creating a CharArrayWriter with the specified initial size.

Methods:

• write(int char) : java.io.CharArrayWriter.write(int char) writes a single character to the Writer. 
  Syntax: 

public void write(int char)
Parameters : 
char : int value of the character to be written.
Return  :
void 

• write(String str, int offset, int maxlen) : java.io.CharArrayWriter.write(String str, int offset, int maxlen) writes some part of the string to the Writer. 
  Syntax: 
  

public void write(String str, int offset, int maxlen)
Parameters : 
str : string to be written to the Writer.
offset : start position of the String
maxlen : maximum length upto which string has to written
Return  :
void 

• write(char[] carray, int offset, int maxlen) : java.io.CharArrayWriter.write(char[] carray, int offset, int maxlen) writes some part of the character array to the Writer. 
  Syntax: 
  

public void write(char[] carray, int offset, int maxlen)
Parameters : 
carray : character to be written to the Writer
offset : start position of the character array
maxlen : maximum no. of the character of the carray has to written
Return  :
void 

• writeTo(Writer out_stream) : java.io.CharArrayWriter.writeTo(Writer out_stream) writes content of the buffer to another specified stream. 
  Syntax : 

public void writeTo(Writer out_stream)
Parameters : 
out_stream : destination stream to be write into
Return  :
void
Exception : 
IOException : In case of I/O error occurs 

• toString() : java.io.CharArrayWriter.toString() returns buffer content as a string from the Writer. 
  Syntax: 

public String toString()
Parameters : 
-----------
Return  :
returns buffer content as a string from the Writer. 

• close() : java.io.StringWriter.close() closes the Writer stream but doesn’t release the buffer 
  Syntax: 

public void close()
Parameters : 
-----------
Return  :
void 

• size() : java.io.StringWriter.size() returns the current size of the buffer as an integer value. 
  Syntax: 

public int size()
Parameters : 
-----------
Return  :
integer value representing the current size of the buffer.

Java code explaining use of CharArrayWriter class methods 

Java

// Java program illustrating the working of CharArrayWriter class methods
// write(int char), toString(), write(char[] carray, int offset, int maxlen)
// write(String str, int offset, int maxlen), size()

import java.io.*;
public class NewClass
{
    public static void main(String[] args) throws IOException
    {

        // Initializing the character array
        char[] geek = {'G', 'E', 'E', 'K', 'S'};
        String geek_str;

        // Initializing the CharArrayWriter
        CharArrayWriter char_array1 = new CharArrayWriter();
        CharArrayWriter char_array2 = new CharArrayWriter();
        CharArrayWriter char_array3 = new CharArrayWriter();

        for(int c = 72; c < 77; c++)
        {
            // Use of write(int char)
            // Writer int value to the Writer
            char_array1.write(c);
        }

        // Use of toString() : returning Buffer content as String
        geek_str = char_array1.toString();
        System.out.println("Using write(int char) : "+ geek_str);


        // Use of write(String str, int offset, int maxlen)
        // writes some part of the string to the Writer.
        char_array2.write(geek_str, 2, 3);

        System.out.println("write(str, offset, maxlen) : "+ char_array2.toString());


        // Use of write(char[] carray, int offset, int maxlen)
        // writes some part of the Char[] geek to the Writer
        char_array3.write(geek, 2, 3);
        System.out.println("write(carray, offset, maxlen) : "+ char_array3.toString());

        // get buffered content as string
        String str = char_array3.toString();


        // Use of writeTo(Writer out_stream)
        char_array3.writeTo(char_array1);

        System.out.println("\nchar_array3 to char_array1 : "+ char_array1.toString());


        // Use of size() method
        System.out.println("\nSize of char_array1 : "+ char_array1.size());
        System.out.println("Size of char_array1 : "+ char_array2.size());
        System.out.println("Size of char_array1 : "+ char_array3.size());

    }
}

Output : 

Using write(int char) : HIJKL
write(str, offset, maxlen) : JKL
write(carray, offset, maxlen) : EKS

char_array3 to char_array1 : HIJKLEKS

Size of char_array1 : 8
Size of char_array1 : 3
Size of char_array1 : 3

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