Odd I/O behavior

Question

Again with the odd behavior. I found the code below while studying for a Java certification exam.
************************ START ************************
import java.io.*;
class OutputTest {
public OutputTest() {
super();
public static void main(java.lang.String[] args) throws IOException {
File file=new File("out");
FileOutputStream fout1=new FileOutputStream(file);
FileOutputStream fout2=new FileOutputStream(file);
PrintWriter pw=new PrintWriter(fout1,true);
fout1.write('A');
fout2.write('B');
pw.println("CD");
fout1.close();
fout2.close();
pw.close();
************************ END ************************
The contents of the file "out" after running this code is "BCD". Does anyone know why write access to one file is allowed by more than one output stream and/or writer? I assumed that the file would be locked when opened by fout1. Is this expected behavior?

Answer 1

A guess on the behaviour.
Both streams are buffered in java. fout1 writes to its buffer, fout2 writes to its buffer. When fout1 closes its buffer is flushed. When fout2 is closed its buffer is flushed which causes it to overwrite the stuff from fout1.
Why it is allowed is a different matter. Perhaps because it is simply to hard to code or too expensive to check. Or simply forgotten. Or because sometimes this behaviour is desired - for example if both flush at the end of every line, then there is no problem.