JDK implementation of OutputStreamWriter writes incorrect number of characters to file with some encodings. Namely with x-IBM949, x-IBM949C and x-IBM970 encodings writer misses each 8193rd character.
I attached source of an example demonstrating this problem. It writes sequences of digits: 0..9 to a file and if we write for example 8194 digit characters to file we'll see at the end of the file:
...123456789013
i.e. next to last character is missing. And we can see that each character after 8192 correctly written characters is missing.