[vbezhenar]

Java has many inefficient parts. For example there's no immutable array concept (or owning concept, like in Rust), so there's a lot of unnecessary array copies happens in JDK. String is not well designed. There was an attempt to abstract String concept into CharSequence, but a lot of code still uses Strings.

I made a similar benchmark. The idea is as follows: we have 2 GB byte array (because arrays in Java have 32 bit limit, LoL) filled with 32..126 values, imitating ASCII text and 13 values imitating newlines.

The first test is simply does XOR the whole array. It's the ideal result which should correspond to memory bandwidth.

The second test wraps this array into ByteArrayInputSteram, converts it into Reader using InputStreamReader with UTF-8 encoding, reads lines using BufferedReader and in the end also XORs every char value.

For 2 GB I have 516 ms as an ideal time (3,8 GB/s which is still almost order of magnitude less than theoretical 19.2 GB/s DDR4 speed) and 3566 ms as a BufferedReader, so you can have almost 7x speed improvement with better implementation.

Benchmark: https://pastebin.com/xMD4W8mn