CharArrayWriter: size()
import java.io.CharArrayReader; import java.io.CharArrayWriter; import java.io.IOException; public class Main { public static void main(String args[]) throws IOException { CharArrayWriter outStream = new CharArrayWriter(); String s = "This is a test."; for (int i = 0; i < s.length(); ++i) outStream.write(s.charAt(i)); System.out.println("outstream: " + outStream); System.out.println("size: " + outStream.size()); CharArrayReader inStream; inStream = new CharArrayReader(outStream.toCharArray()); int ch = 0; StringBuffer sb = new StringBuffer(""); while ((ch = inStream.read()) != -1) sb.append((char) ch); s = sb.toString(); System.out.println(s.length() + " characters were read"); System.out.println("They are: " + s); } }