IO性能测试

package com.example04;
import java.io.*;
import java.nio.ByteBuffer;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;



public class IoTest {
    
    



    /**
     * 测试MappedByte和lO的效率对比
     */
        static int length = 0x8000000; // 128 Mb 一个bit占1B，0x8000000换成十进制为：134217728

        public static void main(String[] args) throws Exception {
    
    
            long start = System.currentTimeMillis();
            // 调用普通io
//            testIO();
            // 调用MappedByteBuffer
//            testMappedByteBuffer();
            // 调用 testFileChannel()
            testFileChannel();
//            // 调用 testFileChannelByteBuffer()
//            testFileChannelByteBuffer();
            long end = System.currentTimeMillis();
            System.out.println("耗时=" + (end - start) + "ms");
            /**
             * 调用 testIO()打印内容：耗时=6218ms/30ms;
             * 调用 testMappedByteBuffer()打印内容：耗时=2132ms /8ms
             * 调用 testFileChannel()打印内容：耗时=703ms
             * 调用 testFileChannelByteBuffer()打印内容：耗时=819ms
             */
        }

        /**
         * 测试0.9G文件，IO的效率
         *
         * @throws IOException
         */
        private static void testIO() throws IOException {
    
    
            File sourceFile = new File("/Users/zhangqin/studycode/test/test.txt");
            byte[] bytes = new byte[1024];  // 和下面方式创建byte[]效率基本一样
//        byte[] bytes = new byte[(int) sourceFile.length()];
            FileInputStream fis = new FileInputStream(sourceFile);
            FileOutputStream fos = new FileOutputStream("/Users/zhangqin/studycode/test/test2.txt");
            int len = -1;
            while ((len = fis.read(bytes)) != -1) {
    
    
                fos.write(bytes, 0, len); // 写入数据
            }
            fis.close();
            fos.close();
        }

        /**
         * 测试0.9G文件，MappedByteBuffer的效率
         *
         * @throws IOException
         */
        private static void testMappedByteBuffer() throws IOException {
    
    
            File sourceFile = new File("/Users/zhangqin/studycode/test/test.txt");
//        byte[] bytes = new byte[1024];  // 和下面方式创建byte[]效率基本一样
            byte[] bytes = new byte[(int) sourceFile.length()];
            RandomAccessFile ra_read = new RandomAccessFile(sourceFile, "r");
            FileChannel fc = new RandomAccessFile("/Users/zhangqin/studycode/test/test3.txt", "rw").getChannel();
            MappedByteBuffer map = fc.map(FileChannel.MapMode.READ_WRITE, 0, sourceFile.length());
            int len = -1;
            while ((len = ra_read.read(bytes)) != -1) {
    
    
                map.put(bytes, 0, len); // 写入数据
            }
            ra_read.close();
            fc.close();
        }

        /**
         * 测试0.9G文件，FileChannel的效率
         *
         * @throws IOException
         */
        private static void testFileChannel() throws IOException {
    
    
            File sourceFile = new File("/Users/zhangqin/studycode/test/test.txt");
            FileInputStream fis = new FileInputStream(sourceFile);
            FileChannel fisChannel = fis.getChannel();
            FileOutputStream fos = new FileOutputStream("/Users/zhangqin/studycode/test/test5.txt");
            FileChannel fosChannel = fos.getChannel();
            fisChannel.transferTo(0, fisChannel.size(), fosChannel);
            fis.close();
            fos.close();
        }

        /**
         * 测试0.9G文件，FileChannel的效率
         *
         * @throws IOException
         */
        private static void testFileChannelByteBuffer() throws IOException {
    
    
            try (FileChannel from = new FileInputStream("/Users/zhangqin/studycode/test/test.txt").getChannel();
                 FileChannel to = new FileOutputStream("/Users/zhangqin/studycode/test/test6.txt").getChannel();
            ) {
    
    
                ByteBuffer bb = ByteBuffer.allocateDirect(1024 * 1024);
                while (true) {
    
    
                    int len = from.read(bb);
                    if (len == -1) {
    
    
                        break;
                    }
                    bb.flip();  // 调用flip之后，读写指针指到缓存头部，切换成读模式
                    to.write(bb);
                    bb.clear();  // 切换成写模式
                }
            } catch (IOException e) {
    
    
                e.printStackTrace();
            }

        }
}