StringWriter

import java.io.IOException;
import java.io.StringWriter;
/*from  j a va2s.c o  m*/
public class Main {
  public static void main(String args[]) throws IOException {
    StringWriter outStream = new StringWriter();
    String s = "This is a test from j a va2s.com.";
    for (int i = 0; i < s.length(); ++i)
      outStream.write(s.charAt(i));
    System.out.println("outstream: " + outStream);
    System.out.println("size: " + outStream.toString().length());
  }
}

outstream: This is a test from j a va2s.com.
size: 33