java 文件读取操作和复制操作（多种方法比较）

package com.file;  
   
import java.io.File;  
import java.io.FileInputStream;  
import java.io.FileNotFoundException;  
import java.io.FileOutputStream;  
import java.io.IOException;  
import java.io.InputStream;  
import java.io.OutputStream;  
import java.nio.ByteBuffer;  
import java.nio.MappedByteBuffer;  
import java.nio.channels.FileChannel;  
import java.text.DateFormat;  
import java.text.SimpleDateFormat;  
import java.util.Date;  
   
/** 
 * file operate 
 * @author ruanpeng 
 * @time 2014-11-11上午9:14:29 
 */ 
public class OperateFileDemo {  
   
    private DateFormat df = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss:SSS");  
    private Date start_time = null;//开始时间  
    private Date end_time = null;//结束时间  
       
    public static void main(String[] args) {  
        OperateFileDemo demo = new OperateFileDemo();  
        demo.operateFile1();  
        demo.operateFile2();  
        demo.operateFile3();  
        demo.fileCopy1();  
        demo.fileCopy2();  
    }  
   
    /** 
     * the first method of reading file 
     */ 
    public void operateFile1(){  
        start_time = new Date();  
        File f = new File("E:"+File.separator+"test.txt");//File.separator——windows is '\'，unix is '/'  
        try {  
            //创建一个流对象  
            InputStream in = new FileInputStream(f);  
            //读取数据，并将读取的数据存储到数组中  
            byte[] b = new byte[(int) f.length()];//数据存储的数组  
            int len = 0;  
            int temp = 0;  
            while((temp = in.read()) != -1){//循环读取数据，未到达流的末尾  
                b[len] = (byte) temp;//将有效数据存储在数组中  
                len ++;  
            }  
               
            System.out.println(new String(b, 0, len, "GBK"));  
            in.close();  
        } catch (FileNotFoundException e) {  
            e.printStackTrace();  
        } catch (IOException e) {  
            e.printStackTrace();  
        }finally{  
            end_time = new Date();  
            System.out.println("==============第一种方式——start_time:"+df.format(start_time));  
            System.out.println("==============第一种方式——end_time:"+df.format(end_time));  
            System.out.println("==============第一种方式总耗时："+(end_time.getTime() - start_time.getTime())+"毫秒");  
        }  
    }  
       
    /** 
     * the second method of reading file 
     */ 
    public void operateFile2(){  
        start_time = new Date();  
        File f = new File("E:"+File.separator+"test.txt");  
        try {  
            InputStream in = new FileInputStream(f);  
            byte[] b = new byte[1024];  
            int len = 0;  
            while((len = in.read(b)) != -1){  
                System.out.println(new String(b, 0, len, "GBK"));  
            }  
            in.close();  
        } catch (FileNotFoundException e) {  
            e.printStackTrace();  
        } catch (IOException e) {  
            e.printStackTrace();  
        }finally{  
            end_time = new Date();  
            System.out.println("==================第二种方式——start_time:"+df.format(start_time));  
            System.out.println("==================第二种方式——end_time:"+df.format(end_time));  
            System.out.println("==================第二种方式总耗时："+(end_time.getTime() - start_time.getTime())+"毫秒");  
        }  
    }  
       
    /** 
     * the third method of reading file(文件读取（Memory mapping-内存映射方式）) 
     * 这种方式的效率是最好的，速度也是最快的，因为程序直接操作的是内存 
     */ 
    public void operateFile3(){  
        start_time = new Date();  
        File f = new File("E:"+File.separator+"test.txt");  
        try {  
            FileInputStream in = new FileInputStream(f);  
            FileChannel chan = in.getChannel();//内存与磁盘文件的通道,获取通道，通过文件通道读写文件。  
            MappedByteBuffer buf = chan.map(FileChannel.MapMode.READ_ONLY, 0, f.length());  
            byte[] b = new byte[(int) f.length()];  
            int len = 0;  
            while(buf.hasRemaining()){  
                b[len] = buf.get();  
                len++;  
            }  
            chan.close();  
            in.close();  
            System.out.println(new String(b,0,len,"GBK"));  
        } catch (FileNotFoundException e) {  
            e.printStackTrace();  
        } catch (IOException e) {  
            e.printStackTrace();  
        }finally{  
            end_time = new Date();  
            System.out.println("======================第三种方式——start_time:"+df.format(start_time));  
            System.out.println("======================第三种方式——end_time:"+df.format(end_time));  
            System.out.println("======================第三种方式总耗时："+(end_time.getTime() - start_time.getTime())+"毫秒");  
        }  
    }  
       
    /** 
     * the first method of copying file 
     */ 
    public void fileCopy1(){  
        start_time = new Date();  
        File f = new File("E:"+File.separator+"test.txt");  
        try {  
            InputStream in = new FileInputStream(f);  
            OutputStream out = new FileOutputStream("F:"+File.separator+"test.txt");  
            int len = 0;  
            while((len = in.read()) != -1){  
                out.write(len);  
            }  
            out.close();  
            in.close();  
        } catch (FileNotFoundException e) {  
            e.printStackTrace();  
        } catch (IOException e) {  
            e.printStackTrace();  
        }finally{  
            end_time = new Date();  
            System.out.println("======================第一种文件复制方式——start_time:"+df.format(start_time));  
            System.out.println("======================第一种文件复制方式——end_time:"+df.format(end_time));  
            System.out.println("======================第一种文件复制方式总耗时："+(end_time.getTime() - start_time.getTime())+"毫秒");  
        }  
    }  
       
    /** 
     * 使用内存映射实现文件复制操作 
     */ 
    public void fileCopy2(){  
        start_time = new Date();  
        File f = new File("E:"+File.separator+"test.txt");  
        try {  
            FileInputStream in = new FileInputStream(f);  
            FileOutputStream out = new FileOutputStream("F:"+File.separator+"test2.txt");  
            FileChannel inChan = in.getChannel();  
            FileChannel outChan = out.getChannel();  
            //开辟缓冲区  
            ByteBuffer buf = ByteBuffer.allocate(1024);  
            while ((inChan.read(buf)) != -1){  
                //重设缓冲区  
                buf.flip();  
                //输出缓冲区  
                outChan.write(buf);  
                //清空缓冲区  
                buf.clear();  
            }  
            inChan.close();  
            outChan.close();  
            in.close();  
            out.close();  
        } catch (FileNotFoundException e) {  
            e.printStackTrace();  
        } catch (IOException e) {  
            e.printStackTrace();  
        }finally{  
            end_time = new Date();  
            System.out.println("======================第二种文件复制方式——start_time:"+df.format(start_time));  
            System.out.println("======================第二种文件复制方式——end_time:"+df.format(end_time));  
            System.out.println("======================第二种文件复制方式总耗时："+(end_time.getTime() - start_time.getTime())+"毫秒");  
        }  
    }  
}