I/O流性能比拼

来源：互联网发布：java环境配置编辑：程序博客网时间：2024/05/29 13:20
package com.nio;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.RandomAccessFile;import java.nio.ByteBuffer;import java.nio.IntBuffer;import java.nio.channels.FileChannel;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            {                // 一秒的10亿分之一，即等于10的负9次方秒                long start = System.nanoTime();                test();                double duration = System.nanoTime() - start;                System.out.format("%.2f\n", duration / 1.0e9);            }            catch (Exception e)            {                e.printStackTrace();            }        }        public abstract void test()            throws Exception;    }    private static Tester[] tests = {    new Tester("Stream Writer")    {        public void test()            throws Exception        {            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("channel writer")    {        @SuppressWarnings("resource")        public void test()            throws Exception        {            FileChannel fc = new RandomAccessFile(new File("temp.tmp"), "rw").getChannel();            ByteBuffer bb = ByteBuffer.allocate(10000);            for (int i = 0; i <= numOfInts; i = i + 10000)            {                for (int j = 0; j < 10000; j++)                {                    bb.asIntBuffer().put(i);                }                fc.write(bb);                bb.flip();                bb.clear();            }            fc.close();        }    }, new Tester("mapped writer")    {        @SuppressWarnings("resource")        public void test()            throws Exception        {            FileChannel fc = new RandomAccessFile(new File("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 Exception        {            DataInputStream dis = new DataInputStream(new BufferedInputStream(new FileInputStream(new File("temp.tmp"))));            for (int i = 0; i < numOfInts; i++)            {                dis.readInt();            }            dis.close();        }    }, new Tester("channel read")    {        @SuppressWarnings("resource")        public void test()            throws Exception        {            FileChannel fc = new RandomAccessFile(new File("temp.tmp"), "rw").getChannel();            ByteBuffer bb = ByteBuffer.allocate(10000);            while (fc.read(bb) != -1)            {                bb.flip();                bb.clear();            }            fc.close();        }    }, new Tester("mapped read")    {        @SuppressWarnings("resource")        public void test()            throws Exception        {            FileChannel fc = new RandomAccessFile(new File("temp.tmp"), "rw").getChannel();            IntBuffer ib = fc.map(FileChannel.MapMode.READ_WRITE, 0, fc.size()).asIntBuffer();            while (ib.hasRemaining())            {                ib.get();            }            fc.close();        }    }, new Tester("Stream read/writer")    {        public void test()            throws Exception        {            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("channel read/writer")    {        @SuppressWarnings("resource")        public void test()            throws Exception        {            FileChannel in = new FileInputStream("temp.tmp").getChannel(), out = new FileOutputStream("temp.tmp2").getChannel();            ByteBuffer buff = ByteBuffer.allocate(10000);// 关乎性能            while (in.read(buff) != -1)            {                buff.flip();                out.write(buff);                buff.clear();            }            in.close();            out.close();        }    }, new Tester("mapped read/writer")    {        @SuppressWarnings("resource")        public void test()            throws Exception        {            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 (Tester test : tests)        {            test.runTest();        }    }}
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