According to the documentation, BufferedReader(Reader) uses a default buffer size, while the second constructor, BufferedReader(Reader, int) allows
BufferedReader(Reader)
BufferedReader(Reader, int)
Ans is 8 KB.
1024 bytes * 8 = 8192 (8 KB) refer class : java.io.BufferedReader
java.io.BufferedReader
private static int defaultCharBufferSize = 8192;