1. 使用頁面大小的普通字節[]的RandomAccessFile 。
2. 緩沖的FileInputStream和FileOutputStream 。
3. 具有頁面大小的ByteBuffer的NIO FileChannel 。
4. 使用NIO和直接MappedByteBuffer映射文件的內存。

編碼

import java.io.*;
import java.nio.ByteBuffer;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;import static java.lang.Integer.MAX_VALUE;
import static java.lang.System.out;
import static java.nio.channels.FileChannel.MapMode.READ_ONLY;
import static java.nio.channels.FileChannel.MapMode.READ_WRITE;public final class TestSequentialIoPerf
{public static final int PAGE_SIZE = 1024 * 4;public static final long FILE_SIZE = PAGE_SIZE * 2000L * 1000L;public static final String FILE_NAME = "test.dat";public static final byte[] BLANK_PAGE = new byte[PAGE_SIZE];public static void main(final String[] arg) throws Exception{preallocateTestFile(FILE_NAME);for (final PerfTestCase testCase : testCases){for (int i = 0; i < 5; i++){System.gc();long writeDurationMs = testCase.test(PerfTestCase.Type.WRITE,FILE_NAME);System.gc();long readDurationMs = testCase.test(PerfTestCase.Type.READ,FILE_NAME);long bytesReadPerSec = (FILE_SIZE * 1000L) / readDurationMs;long bytesWrittenPerSec = (FILE_SIZE * 1000L) / writeDurationMs;out.format("%s\twrite=%,d\tread=%,d bytes/sec\n",testCase.getName(),bytesWrittenPerSec, bytesReadPerSec);}}deleteFile(FILE_NAME);}private static void preallocateTestFile(final String fileName)throws Exception{RandomAccessFile file = new RandomAccessFile(fileName, "rw");for (long i = 0; i < FILE_SIZE; i += PAGE_SIZE){file.write(BLANK_PAGE, 0, PAGE_SIZE);}file.close();}private static void deleteFile(final String testFileName) throws Exception{File file = new File(testFileName);if (!file.delete()){out.println("Failed to delete test file=" + testFileName);out.println("Windows does not allow mapped files to be deleted.");}}public abstract static class PerfTestCase{public enum Type { READ, WRITE }private final String name;private int checkSum;public PerfTestCase(final String name){this.name = name;}public String getName(){return name;}public long test(final Type type, final String fileName){long start = System.currentTimeMillis();try{switch (type){case WRITE:{checkSum = testWrite(fileName);break;}case READ:{final int checkSum = testRead(fileName);if (checkSum != this.checkSum){final String msg = getName() +" expected=" + this.checkSum +" got=" + checkSum;throw new IllegalStateException(msg);}break;}}}catch (Exception ex){ex.printStackTrace();}return System.currentTimeMillis() - start;}public abstract int testWrite(final String fileName) throws Exception;public abstract int testRead(final String fileName) throws Exception;}private static PerfTestCase[] testCases ={new PerfTestCase("RandomAccessFile"){public int testWrite(final String fileName) throws Exception{RandomAccessFile file = new RandomAccessFile(fileName, "rw");final byte[] buffer = new byte[PAGE_SIZE];int pos = 0;int checkSum = 0;for (long i = 0; i < FILE_SIZE; i++){byte b = (byte)i;checkSum += b;buffer[pos++] = b;if (PAGE_SIZE == pos){file.write(buffer, 0, PAGE_SIZE);pos = 0;}}file.close();return checkSum;}public int testRead(final String fileName) throws Exception{RandomAccessFile file = new RandomAccessFile(fileName, "r");final byte[] buffer = new byte[PAGE_SIZE];int checkSum = 0;int bytesRead;while (-1 != (bytesRead = file.read(buffer))){for (int i = 0; i < bytesRead; i++){checkSum += buffer[i];}}file.close();return checkSum;}},new PerfTestCase("BufferedStreamFile"){public int testWrite(final String fileName) throws Exception{int checkSum = 0;OutputStream out = new BufferedOutputStream(new FileOutputStream(fileName));for (long i = 0; i < FILE_SIZE; i++){byte b = (byte)i;checkSum += b;out.write(b);}out.close();return checkSum;}public int testRead(final String fileName) throws Exception{int checkSum = 0;InputStream in = new BufferedInputStream(new FileInputStream(fileName));int b;while (-1 != (b = in.read())){checkSum += (byte)b;}in.close();return checkSum;}},new PerfTestCase("BufferedChannelFile"){public int testWrite(final String fileName) throws Exception{FileChannel channel = new RandomAccessFile(fileName, "rw").getChannel();ByteBuffer buffer = ByteBuffer.allocate(PAGE_SIZE);int checkSum = 0;for (long i = 0; i < FILE_SIZE; i++){byte b = (byte)i;checkSum += b;buffer.put(b);if (!buffer.hasRemaining()){buffer.flip();channel.write(buffer);buffer.clear();}}channel.close();return checkSum;}public int testRead(final String fileName) throws Exception{FileChannel channel = new RandomAccessFile(fileName, "rw").getChannel();ByteBuffer buffer = ByteBuffer.allocate(PAGE_SIZE);int checkSum = 0;while (-1 != (channel.read(buffer))){buffer.flip();while (buffer.hasRemaining()){checkSum += buffer.get();}buffer.clear();}return checkSum;}},new PerfTestCase("MemoryMappedFile"){public int testWrite(final String fileName) throws Exception{FileChannel channel = new RandomAccessFile(fileName, "rw").getChannel();MappedByteBuffer buffer = channel.map(READ_WRITE, 0,Math.min(channel.size(), MAX_VALUE));int checkSum = 0;for (long i = 0; i < FILE_SIZE; i++){if (!buffer.hasRemaining()){buffer = channel.map(READ_WRITE, i,Math.min(channel.size() - i , MAX_VALUE));}byte b = (byte)i;checkSum += b;buffer.put(b);}channel.close();return checkSum;}public int testRead(final String fileName) throws Exception{FileChannel channel = new RandomAccessFile(fileName, "rw").getChannel();MappedByteBuffer buffer = channel.map(READ_ONLY, 0,Math.min(channel.size(), MAX_VALUE));int checkSum = 0;for (long i = 0; i < FILE_SIZE; i++){if (!buffer.hasRemaining()){buffer = channel.map(READ_WRITE, i,Math.min(channel.size() - i , MAX_VALUE));}checkSum += buffer.get();}channel.close();return checkSum;}},};
}

結果

400MB file
===========
RandomAccessFile write=294,041,636 read=1,494,890,510 bytes/sec

BufferedStreamFile寫入= 98,178,331讀取= 286,433,566字節/秒
BufferedStreamFile寫入= 100,244,738讀取= 288,857,545字節/秒
BufferedStreamFile寫入= 82,948,562讀取= 154,100,827字節/秒 BufferedStreamFile寫入= 108,503,311讀取= 153,869,271字節/秒 BufferedStreamFile寫入= 113,055,478讀取= 152,608,047字節/秒

BufferedChannelFile寫入= 228,443,948讀取= 356,173,913字節/秒
BufferedChannelFile寫入= 265,629,053讀取= 374,063,926字節/秒
BufferedChannelFile寫= 223,825,136讀= 1,539,849,624字節/秒BufferedChannelFile寫= 232,992,036讀= 1,539,849,624字節/秒BufferedChannelFile寫= 212,779,220讀= 1,534,082,397字節/秒 MemoryMappedFile寫入= 300,955,180讀取= 305,899,925字節/秒 MemoryMappedFile寫入= 313,149,847讀取= 310,538,286字節/秒 MemoryMappedFile寫入= 326,374,501讀取= 303,857,566字節/秒 MemoryMappedFile寫入= 327,680,000讀取= 304,535,315字節/秒 MemoryMappedFile寫入= 326895450讀取= 303632320字節/秒

8GB文件
============
RandomAccessFile寫入= 167,402,321讀取= 251,922,012字節/秒 RandomAccessFile寫入= 193,934,802讀取= 257,052,307字節/秒 RandomAccessFile寫入= 192,948,159讀取= 248,460,768字節/秒 RandomAccessFile寫入= 191,814,180讀取= 245,225,408字節/秒 RandomAccessFile寫入= 190,635,762讀取= 275,315,073字節/秒

BufferedStreamFile寫入= 154,823,102讀取= 248,355,313字節/秒
BufferedStreamFile寫入= 152,083,913讀取= 253,418,301字節/秒
BufferedStreamFile寫入= 133,099,369讀取= 146,056,197字節/秒 BufferedStreamFile寫入= 131,065,708讀取= 146,217,827字節/秒 BufferedStreamFile寫入= 132694052讀取= 148116004字節/秒

BufferedChannelFile寫入= 186703740讀取= 215075218字節/秒
BufferedChannelFile寫入= 190,591,410讀取= 211,030,680字節/秒BufferedChannelFile寫入= 187,220,038讀取= 223,087,606字節/秒
BufferedChannelFile寫入= 191,585,397讀取= 221,297,747字節/秒 BufferedChannelFile寫入= 192,653,214讀取= 211,789,038字節/秒

MemoryMappedFile寫入= 123,023,322讀取= 231,530,156字節/秒
MemoryMappedFile寫入= 121,961,023讀取= 230,403,600字節/秒
MemoryMappedFile寫入= 123,317,778讀取= 229,899,250字節/秒 MemoryMappedFile寫入= 121,472,738讀取= 231,739,745字節/秒 MemoryMappedFile寫入= 120,362,615讀取= 231,190,382字節/秒

分析