介绍一下Java NIO，NIO读取文件都有哪些方法

NIO也就是New I/O,是一组扩展Java IO *** 作的API集， 于Java 1.4起被引入，Java 7中NIO又提供了一些新的文件系统API，叫NIO2.

NIO2提供两种主要的文件读取方法：

使用buffer和channel类

使用Path 和 File 类

NIO读取文件有以下三种方式：

1. 旧的NIO方式，使用BufferedReader

import java.io.BufferedReader

import java.io.FileReader

import java.io.IOException

public class WithoutNIOExample

{

public static void main(String[] args)

{

BufferedReader br = null

String sCurrentLine = null

try

{

br = new BufferedReader(

new FileReader("test.txt"))

while ((sCurrentLine = br.readLine()) != null)

{

System.out.println(sCurrentLine)

}

}

catch (IOException e)

{

e.printStackTrace()

}

finally

{

try

{

if (br != null)

br.close()

} catch (IOException ex)

{

ex.printStackTrace()

}

}

}

}

2. 使用buffer读取小文件

import java.io.IOException

import java.io.RandomAccessFile

import java.nio.ByteBuffer

import java.nio.channels.FileChannel

public class ReadFileWithFileSizeBuffer

{

public static void main(String args[])

{

try

{

RandomAccessFile aFile = new RandomAccessFile(

"test.txt","r")

FileChannel inChannel = aFile.getChannel()

long fileSize = inChannel.size()

ByteBuffer buffer = ByteBuffer.allocate((int) fileSize)

inChannel.read(buffer)

buffer.rewind()

buffer.flip()

for (int i = 0i <fileSizei++)

{

System.out.print((char) buffer.get())

}

inChannel.close()

aFile.close()

}

catch (IOException exc)

{

System.out.println(exc)

System.exit(1)

}

}

}

3. 分块读取大文件

import java.io.IOException

import java.io.RandomAccessFile

import java.nio.ByteBuffer

import java.nio.channels.FileChannel

public class ReadFileWithFixedSizeBuffer

{

public static void main(String[] args) throws IOException

{

RandomAccessFile aFile = new RandomAccessFile

("test.txt", "r")

FileChannel inChannel = aFile.getChannel()

ByteBuffer buffer = ByteBuffer.allocate(1024)

while(inChannel.read(buffer) >0)

{

buffer.flip()

for (int i = 0i <buffer.limit()i++)

{

System.out.print((char) buffer.get())

}

buffer.clear()// do something with the data and clear/compact it.

}

inChannel.close()

aFile.close()

}

}

4. 使用MappedByteBuffer读取文件

import java.io.RandomAccessFile

import java.nio.MappedByteBuffer

import java.nio.channels.FileChannel

public class ReadFileWithMappedByteBuffer

{

public static void main(String[] args) throws IOException

{

RandomAccessFile aFile = new RandomAccessFile

("test.txt", "r")

FileChannel inChannel = aFile.getChannel()

MappedByteBuffer buffer = inChannel.map(FileChannel.MapMode.READ_ONLY, 0, inChannel.size())

buffer.load()?

for (int i = 0i <buffer.limit()i++)

{

System.out.print((char) buffer.get())

}

buffer.clear()// do something with the data and clear/compact it.

inChannel.close()

aFile.close()

}

}

OOM 说你的程序内存溢出了

你这个文件如果很大的话,建议用inputStreamReader

这个包装类,可以用指定的编码去读取文件

用法:

File file = new File("文件路径")

InputStreamReader isr = new InputStreamReader(new FileInputStream(file),"GBK")

更详细的用法,建议查看api

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