[java][nio]Stream与MappedByteBuffer的性能比较

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.IntBuffer;
import java.nio.channels.FileChannel;
/**
 * 
 * Stream与MappedByteBuffer的性能对比.
 * 
Stream Write : 3.59
Mapped Write : 0.27
Stream Read : 3.17
Mapped Read : 0.21
Stream Read/Write : 30.86
Mapped Read/Write : 0.15
 * 
 *
 */
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 void runTest(){
			System.out.print(name + " : ");
			try {
				long start = System.nanoTime();
				test();
				double duration = System.nanoTime() - start;
				System.out.format("%.2f\n", duration/1.0e9);
			} 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("d:\\temp.tmp"))));
				for(int i = 0; i < numOfInts; i++){
					dos.writeInt(i);
				}
				if(dos != null){
					dos.close();
				}
			}
		},
		new Tester("Mapped Write"){
			public void test() throws IOException{
				FileChannel fc = new RandomAccessFile("d:\\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);
				}
				if(fc != null){
					fc.close();
				}
			}
		},
		new Tester("Stream Read"){
			public void test() throws IOException{
				DataInputStream dis = new DataInputStream(new BufferedInputStream(new FileInputStream(new File("d:\\temp.tmp"))));
				for(int i = 0; i < numOfInts; i++){
					dis.readInt();
				}
				if(dis != null){
					dis.close();
				}
			}
		},
		new Tester("Mapped Read"){
			public void test() throws IOException{
				FileChannel fc = new FileInputStream("d:\\temp.tmp").getChannel();
				IntBuffer ib = fc.map(FileChannel.MapMode.READ_ONLY, 0, fc.size()).asIntBuffer();
				while(ib.hasRemaining()){
					ib.get();
				}
				if(fc != null){
					fc.close();
				}
			}
		},
		new Tester("Stream Read/Write"){
			public void test() throws IOException{
				RandomAccessFile raf = new RandomAccessFile("d:\\temp.tmp","rw");
				raf.writeInt(1);
				for(int i = 0; i < numOfUbuffInts; i++){
					raf.seek(raf.length() - 4);//绝对定位，离文件头的字节数.skipBytes相对定位，跳过指定长度。
					raf.writeInt(raf.readInt());
				}
				if(raf != null){
					raf.close();
				}
			}
		},
		new Tester("Mapped Read/Write"){
			public void test() throws IOException{
				FileChannel fc = new RandomAccessFile("d:\\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));
				}
				if(fc != null){
					fc.close();
				}
			}
		}
	};
	
	public static void main(String[] args) {
		for(Tester tst : tests){
			tst.runTest();
		}
	}
}