JAVA NIO(三) 三种文件的复制方法与效率对比

文件的复制最能体现io效率了.因为既需要读取数据还需要写出到硬盘中,下面提供了三种文件复制的方法 可以对比一下 直接缓冲区与非直接缓冲区的效率对比.

public class Nio {

public static void main(String[] args) throws IOException {
nioCopyTest1();
nioCopyTest2();
nioCopyTest3();
}

/**通道之间的数据传输(直接缓冲区的模式)
*
*/

private static void   nioCopyTest3() throws IOException {
long startTime = System.currentTimeMillis();

FileChannel inChannel = FileChannel.open(Paths.get("E:\\ 1.avi"), StandardOpenOption.READ);

FileChannel outChennel = FileChannel.open(Paths.get("E:\\ 13.avi"),StandardOpenOption.WRITE,StandardOpenOption.READ,StandardOpenOption.CREATE_NEW);

outChennel.transferFrom(inChannel,0,inChannel.size());

long end = System.currentTimeMillis();
System.out.println("nioCopyTest3耗费时间:"+(end-startTime));
}

/**
* 使用直接缓冲区完成文件的复制(内存映射文件)
*/
private static void  nioCopyTest2() throws IOException {
long startTime = System.currentTimeMillis();

FileChannel inChannel = FileChannel.open(Paths.get("E:\\ 1.avi"), StandardOpenOption.READ);

FileChannel outChennel = FileChannel.open(Paths.get("E:\\ 12.avi"),StandardOpenOption.WRITE,StandardOpenOption.READ,StandardOpenOption.CREATE_NEW);

//内存映射文件(什么模式 从哪开始 到哪结束)
MappedByteBuffer inMappeBuf = inChannel.map(FileChannel.MapMode.READ_ONLY,0,inChannel.size());
MappedByteBuffer outMappeBuf =  outChennel.map(FileChannel.MapMode.READ_WRITE,0,inChannel.size());

//直接都缓冲区进行数据的读写操作

byte[] dst = new byte[inMappeBuf.limit()];
inMappeBuf.get(dst);
outMappeBuf.put(dst);

inChannel.close();
outChennel.close();
long end = System.currentTimeMillis();
System.out.println("nioCopyTest2耗费时间:"+(end-startTime));
}

/**
*  非直接缓冲区 文件的复制
* @throws IOException
*/
private static void nioCopyTest1()throws IOException {
long startTime = System.currentTimeMillis();
FileInputStream fileInputStream = new FileInputStream(new File("E:\\ 1.avi"));
FileOutputStream fileOutputStream = new FileOutputStream("E:\\ 11.avi");

//获取通道
FileChannel inChannel = fileInputStream.getChannel();
FileChannel outChanel = fileOutputStream.getChannel();

//分配缓冲区的大小
ByteBuffer buf = ByteBuffer.allocate(1024);

//将通道中的数据存入缓冲区
while (inChannel.read(buf) != -1) {
buf.flip();//切换读取数据的模式
outChanel.write(buf);
buf.clear();
}
outChanel.close();
inChannel.close();
fileInputStream.close();
fileOutputStream.close();
long end = System.currentTimeMillis();
System.out.println("nioCopyTest1耗费时间:"+(end-startTime));
}
}

控制台输出:

nioCopyTest1耗费时间:1417
nioCopyTest2耗费时间:142

nioCopyTest3耗费时间:68

直接缓冲不需要文件的复制拷贝 所以大大增加效率 其中第三种方法通道之间的文件传输 速度最快了直接在通道中完成.