simple experiment for http://stackoverflow.com/questions/6114697/what-would-be-the-fastest-way-to-read-integers-from-a-file-in-java

ScannerTest.java

import java.io.IOException;
import java.io.StringReader;
import java.util.Random;
import java.util.Scanner;

public class ScannerTest {
	public static void main(String[] args) throws IOException {
		int chars = (37 * 1000 * 1000);

		StringBuilder buf = new StringBuilder(chars);
		Random rand = new Random();

		System.out.println("start appending " + chars + " chars");
		while (buf.length() < chars) {
			buf.append(rand.nextInt(9999)).append(" ");
		}

		System.out.println("buf to string");
		String str = buf.toString();

		for (int round = 0; round < 5; round++) {

			Scanner scan = new Scanner(str);

			long sum = 0;

			System.out.println("scanning");
			long start = System.currentTimeMillis();
			while (scan.hasNext()) {
				sum += scan.nextInt();
			}
			long time = System.currentTimeMillis() - start;
			System.out.println("finished " + time + "ms " + sum);

			System.out.println("reading");
			StringReader r = new StringReader(str);
			sum = 0;

			int next;
			int current = 0;
			while ((next = r.read()) > 0) {
				if (next == ' ') {
					sum += current;
					current = 0;
				} else {
					current = current * 10 + (next - '0');
				}
			}
			time = System.currentTimeMillis() - start;
			System.out.println("finished " + time + "ms " + sum);
		}
	}
}