import java.io.*;
import java.nio.*;
import java.nio.channels.*;

/**
 * Compares the performance of streaming data to disk vs using memory mapped files.
 *.
public class MappedIO {
    private static int numOfInts = 4000000;
    private static int numOfUbuffInts = 200000;
    private abstract static class Tester {
        private String name;
        public Tester(String name) { this.name = name; }
        public long runTest() {
            System.out.print(name + ": ");
            try {
                long startTime = System.currentTimeMillis();
                test();
                long endTime = System.currentTimeMillis();
                return (endTime - startTime);
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
        public abstract void test() throws IOException;
    }
    private static Tester[] tests = {
        new Tester("Stream Write") {
            public void test() throws IOException {
                DataOutputStream dos = new DataOutputStream(
                    new BufferedOutputStream(
                        new FileOutputStream(new File("temp.tmp"))));
                for(int i = 0; i < numOfInts; i++)
                    dos.writeInt(i);
                dos.close();
            }
        },
        new Tester("Mapped Write") {
            public void test() throws IOException {
                FileChannel fc =
                    new RandomAccessFile("temp.tmp", "rw")
                        .getChannel();
                IntBuffer ib = fc.map(
                    FileChannel.MapMode.READ_WRITE, 0, fc.size())
                    .asIntBuffer();
                for(int i = 0; i < numOfInts; i++)
                    ib.put(i);
                fc.close();
            }
        },
        new Tester("Stream Read") {
            public void test() throws IOException {
                DataInputStream dis = new DataInputStream(
                    new BufferedInputStream(
                        new FileInputStream("temp.tmp")));
                for(int i = 0; i < numOfInts; i++)
                    dis.readInt();
                dis.close();
            }
        },
        new Tester("Mapped Read") {
            public void test() throws IOException {
                FileChannel fc = new FileInputStream(
                    new File("temp.tmp")).getChannel();
                IntBuffer ib = fc.map(
                    FileChannel.MapMode.READ_ONLY, 0, fc.size())
                    .asIntBuffer();
                while(ib.hasRemaining())
                    ib.get();

                fc.close();
            }
        },
        new Tester("Stream Read/Write") {
            public void test() throws IOException {
                RandomAccessFile raf = new RandomAccessFile(
                    new File("temp.tmp"), "rw");
                raf.writeInt(1);
                for(int i = 0; i < numOfUbuffInts; i++) {
                    raf.seek(raf.length() - 4);
                    raf.writeInt(raf.readInt());
                }
                raf.close();
            }
        },
        new Tester("Mapped Read/Write") {
            public void test() throws IOException {
                FileChannel fc = new RandomAccessFile(
                    new File("temp.tmp"), "rw").getChannel();
                IntBuffer ib = fc.map(
                    FileChannel.MapMode.READ_WRITE, 0, fc.size())
                    .asIntBuffer();
                ib.put(0);
                for(int i = 1; i < numOfUbuffInts; i++)
                    ib.put(ib.get(i - 1));

                fc.close();
            }
        }
    };
    public static void main(String[] args) {
        for(int i = 0; i < tests.length; i++)
            System.out.println(tests[i].runTest());
    }
}