J:\jtest>java -version
java version "1.4.0-beta"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.0-beta-b56)
Java HotSpot(TM) Client VM (build B56, mixed mode)


Consider the following program:

import java.io.*;
public class OpenApp {

    public static void main(String[] args) throws Throwable{
        OutputStream outStream = new FileOutputStream("tmp");
        Writer wr = new OutputStreamWriter(outStream);
        wr.write("ab");
        wr.close();

        outStream = new FileOutputStream("tmp",true);
        wr = new OutputStreamWriter(outStream);
        wr.write("cd");
        wr.close();
    }
}

J:\jtest>javac OpenApp.java
J:\jtest>java OpenApp
J:\jtest>type tmp
cd

The second open of the file does not append even if it is told
to do so.