The java.io.FilterOutputStream constructor FilterOutputStream(OutputStream out)
accepts and does not check null parameter. It creates a FilterOutputStream
object with an invalid state: every call to this object results in throwing
undocumented NullPointerException.

Here is the example demonstrating this bug

_______________________Test.java ______________________________________
import java.io.*;

public class Test {

public static void main( String argv[] ) {

 MyFilterOutputStream os = new MyFilterOutputStream(null);
 try {
   os.write(25);
   System.out.println("No exceptions - rather strange but alright");
 } catch (IOException e) {
   System.out.println("IOException is thrown - possible result");
 } catch (Throwable e) {
   System.out.println(e+" is thrown - this is not allowed");
 }
}

}

class MyFilterOutputStream extends FilterOutputStream {
public MyFilterOutputStream (OutputStream out) { super(out); }
}
_____________________Output_________________________________________

java.lang.NullPointerException is thrown - this is not allowed
____________________________________________________________________