[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 : 3.59Mapped Write : 0.27Stream Read : 3.17Mapped Read : 0.21Stream Read/Write : 30.86Mapped 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();}}}
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