casting error on ArrayList

I'm getting a cast error "java.lang.ClassCastException: [Ljava.lang.Object;
incompatible with [Ljava.lang.String;" and not sure why and how to resolve
it. Help. . . ..

ArrayList<String> rs = new ArrayList<String>( 20 );

String str;

bin= new BufferedReader(new InputStreamReader(process.getInputStream()));

while ((str = bin.readLine()) != null) {

rs.add(str);

}


return (String[]) rs.toArray(); // =======> Getting the casting error:

}