使用FileChannel通道读写文件

使用FileChannel通道读写文件

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;

public class ChannelTest {
public static void main(String[] args) {
	// TODO Auto-generated method stub
	ChannelTest ct = new ChannelTest();
	ct.writeFile();
	ct.readFile();
}
//写入文本文件
public void writeFile() {
	//1 创建输出流
	FileOutputStream fos = null;
	//2 获取通道
	FileChannel fc = null;
	try {
		//初始化输出流
		fos = new FileOutputStream("e:\\ex\\out.txt");
		//获取通道。通道是通过流获得的（注意！！！）
		fc = fos.getChannel();
		//3 创建缓冲区
		ByteBuffer buffer = ByteBuffer.allocate(1024);
		//4 向缓冲区写入数据，把字符转成字节并写入缓冲区
		buffer.put("Whatever is worth doing is worth doing well.".getBytes());
		//改状态
		buffer.flip();
		//5 通过通道写入目标文件
		//FileChannel类中的.write()方法：将字节序列从给定的缓冲区写入此通道。
		fc.write(buffer);
		//6 关闭资源（在下面的finally中判断关闭）
		
	} catch (FileNotFoundException e) {
		// TODO Auto-generated catch block
		e.printStackTrace();
	} catch (IOException e) {
		// TODO Auto-generated catch block
		e.printStackTrace();
	}finally{
		try {
			if(fc!=null) {
				fc.close();
			}
			if(fos!=null) {
				fos.close();
			}
		}catch(IOException ex){
			
		}
	}
}
public void readFile() {
	//创建流
	FileInputStream fis = null;
	FileChannel fc = null;
	
	try {
		fis = new FileInputStream("e:\\ex\\out.txt");
		fc = fis.getChannel();
		ByteBuffer buffer = ByteBuffer.allocate(1024);
		int length = fc.read(buffer);
		buffer.flip();
		byte[] ary = new byte[length];
		//把缓冲区的内容获取后存入ary数组中
		buffer.get(ary);
		//clear并未清除内容，而是把position置0（注意！！！）
		buffer.clear();
		System.out.println(new String(ary));
		
	} catch (FileNotFoundException e) {
		// TODO Auto-generated catch block
		e.printStackTrace();
	} catch (IOException e) {
		// TODO Auto-generated catch block
		e.printStackTrace();
	}finally {
		try {
			if(fc!=null) {
				fc.close();
			}
			if(fis!=null) {
				fis.close();
			}
		}catch(IOException e) {
			e.printStackTrace();
		}
	  }
	}
 }