異なる方法でファイルを読み書きするパフォーマンスの比較

注意:bufferedReadの読み書き速度が最も速い

package com.test;

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

public class Test {
	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("BufferReader   Read") {
		public void test() throws IOException {
			File file = new File("temp.tmp");
			InputStreamReader read = new InputStreamReader(
			new FileInputStream(file), "UTF-8");
			BufferedReader reader = new BufferedReader(read);
			String line;
			while ((line = reader.readLine()) != null){
				
			}
			read.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());
	}