ReadLineBenchmark.java

import java.io.*;

public class ReadLineBenchmark {
    long volume = 0;

    static class StringSlice implements CharSequence {
        private final String str;
        private final int idx;
        private final int end;

        StringSlice(String str, int idx, int end) {
            this.str = str;
            this.idx = idx;
            this.end = end;
        }

        @Override
        public int length() {
            return end - idx;
        }

        @Override
        public char charAt(int index) {
            return str.charAt(idx + index);
        }

        @Override
        public CharSequence subSequence(int start, int end) {
            return new StringSlice(str, idx + start, idx + end);
        }

        @Override
        public String toString() {
            return str.substring(idx, end);
        }
    }


    public void parseLine(String s) {
        volume += s.length();
    }

    public void parseLine(CharSequence s) {
        volume += s.length();
    }

    public static StringBuilder scanFile(String location) throws IOException {
        FileReader fr = new FileReader(location);
        BufferedReader bf = new BufferedReader(fr);
        StringBuilder sb = new StringBuilder();
        bf.lines().forEach(s -> sb.append(s).append('\n'));
        bf.close();
        return sb;
    }

    public void readString(String data) throws IOException {
        StringReader fr = new StringReader(data);
        BufferedReader bf = new BufferedReader(fr);
        bf.lines().forEach(s -> parseLine(s));
        bf.close();
    }

    public void readStringSubstring(String data) throws IOException {
        int lastIdx = 0;
        for (int idx = data.indexOf('\n'); idx > -1; idx = data.indexOf('\n', lastIdx)) {
            parseLine(data.substring(lastIdx, idx));
            lastIdx = idx + 1;
        }
        parseLine(data.substring(lastIdx));
    }

    public void readStringCustomSlice(String data) throws IOException {
        int lastIdx = 0;
        for (int idx = data.indexOf('\n'); idx > -1; idx = data.indexOf('\n', lastIdx)) {
            parseLine(new StringSlice(data, lastIdx, idx));
            lastIdx = idx + 1;
        }
        parseLine(new StringSlice(data, lastIdx, data.length()));
    }

    public void readStringSubsequence(String data) throws IOException {
        int lastIdx = 0;
        for (int idx = data.indexOf('\n'); idx > -1; idx = data.indexOf('\n', lastIdx)) {
            parseLine(data.subSequence(lastIdx, idx));
            lastIdx = idx + 1;
        }
        parseLine(data.subSequence(lastIdx, data.length()));
    }

    public void readStringLines(String data) {
        data.lines().forEach(this::parseLine);
    }

    public static void main(String[] args) throws IOException {
        StringBuilder stringBuffer = scanFile("test.txt");
        String data = stringBuffer.toString();
        for (int k = 0; k < 50; k++) {
            ReadLineBenchmark d = new ReadLineBenchmark();
            long bef = System.currentTimeMillis();
            d.readStringCustomSlice(data);
            long aft = System.currentTimeMillis();
            long fz = new File("test.txt").length();
            // we need the leave time for the JIT
            if (k >= 40)
                System.out.format("speed: %.3f GB/s\n", fz / (1024.0 * 1024.0 * 1024.0) / ((aft - bef) / 1000.0));
        }
    }
}