File---文件切割和合并

1 好处在于看完下面代码 易于理解hadoop filesplit切割这块具体流程：

2 文件切割 操作流： RandomAccessFile  输出流： BufferedOutputStream

package com.bjsxt.io.others;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
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.RandomAccessFile;
import java.io.SequenceInputStream;
import java.util.ArrayList;
import java.util.List;
import java.util.Vector;

import com.bjsxt.io.util.FileUtil;
public class SplitFile {
	//文件的路径
	private String filePath;
	//文件名
	private String fileName;
	//文件大小
	private long length;
	//块数
	private int size;
	//每块的大小
	private long blockSize;
	//分割后的存放目录
	private String destBlockPath;
	//每块的名称
	private List<String> blockPath;
	
	public SplitFile(){
		blockPath = new ArrayList<String>();
	}
	public SplitFile(String filePath,String destBlockPath){
		this(filePath,destBlockPath,1024);		
	}
	public SplitFile(String filePath,String destBlockPath,long blockSize){
		this();
		this.filePath= filePath;
		this.destBlockPath =destBlockPath;
		this.blockSize=blockSize;
		init();
	}
	
	/**
	 * 初始化操作 计算 块数、确定文件名
	 */
	public void init(){
		File src =null;
		//健壮性
		if(null==filePath ||!(((src=new File(filePath)).exists()))){
			return;
		}
		if(src.isDirectory()){
			return ;
		}
		//文件名
		this.fileName =src.getName();
		
		//计算块数 实际大小 与每块大小
		this.length = src.length();
		//修正 每块大小
		if(this.blockSize>length){
			this.blockSize =length;
		}
		//确定块数		
		size= (int)(Math.ceil(length*1.0/this.blockSize));
		//确定文件的路径
		initPathName();
	}
	
	private void initPathName(){
		for(int i=0;i<size;i++){
			this.blockPath.add(destBlockPath+"/"+this.fileName+".part"+i);
		}
	}
	
	/**
	 * 文件的分割
	 * 0)、第几块
	 * 1、起始位置
	 * 2、实际大小
	 * @param destPath 分割文件存放目录
	 */
	public void split(){	
		long beginPos =0;  //起始点
		long actualBlockSize =blockSize; //实际大小		
		//计算所有块的大小、位置、索引
		for(int i=0;i<size;i++){
			if(i==size-1){ //最后一块
				actualBlockSize =this.length-beginPos;
			}			
			spiltDetail(i,beginPos,actualBlockSize);
			beginPos+=actualBlockSize; //本次的终点，下一次的起点
		}
		
	}
	/**
	 * 文件的分割 输入 输出
	 * 文件拷贝
	 * @param idx 第几块
	 * @param beginPos 起始点
	 * @param actualBlockSize 实际大小
	 */
	private void spiltDetail(int idx,long beginPos,long actualBlockSize){
		//1、创建源
		File src = new File(this.filePath);  //源文件
		File dest = new File(this.blockPath.get(idx)); //目标文件
		//2、选择流
		RandomAccessFile raf = null;  //输入流
		BufferedOutputStream bos=null; //输出流
		try {
			raf=new RandomAccessFile(src,"r")// // 以只读方式打开 
			bos =new BufferedOutputStream(new FileOutputStream(dest));
			
			//读取文件
			raf.seek(beginPos);
			//缓冲区
			byte[] flush = new byte[1024];
			//接收长度
			int len =0;
			while(-1!=(len=raf.read(flush))){				
				if(actualBlockSize-len>=0){ //查看是否足够
					//写出
					bos.write(flush, 0, len);
					actualBlockSize-=len; //剩余量
				}else{ //写出最后一次的剩余量
					bos.write(flush, 0, (int)actualBlockSize);
					break;
				}
			}
			
			
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}finally{
			FileUtil.close(bos,raf);
		}
		
	}
	/**
	 * 文件的合并
	 */
	public void merge(String destPath){
		//创建源
		File dest =new File(destPath);
		//选择流
		BufferedOutputStream bos=null; //输出流
		SequenceInputStream sis =null ;//输入流
		//创建一个容器
		Vector<InputStream> vi = new Vector<InputStream>();		
		try {
			for (int i = 0; i < this.blockPath.size(); i++) {
				vi.add(new BufferedInputStream(new FileInputStream(new File(this.blockPath.get(i)))));
			}	
			bos =new BufferedOutputStream(new FileOutputStream(dest,true)); //追加
			sis=new SequenceInputStream(vi.elements());			
				
			//缓冲区
			byte[] flush = new byte[1024];
			//接收长度
			int len =0;
			while(-1!=(len=sis.read(flush))){						
				bos.write(flush, 0, len);
			}
			bos.flush();
			FileUtil.close(sis);
		} catch (Exception e) {
		}finally{
			FileUtil.close(bos);
		}		
		
	}
	/**
	 * 文件的合并
	 */
	public void merge1(String destPath){
		//创建源
		File dest =new File(destPath);
		//选择流
		BufferedOutputStream bos=null; //输出流
		try {
			bos =new BufferedOutputStream(new FileOutputStream(dest,true)); //追加
			BufferedInputStream bis = null;
			for (int i = 0; i < this.blockPath.size(); i++) {
				bis = new BufferedInputStream(new FileInputStream(new File(this.blockPath.get(i))));
				
				//缓冲区
				byte[] flush = new byte[1024];
				//接收长度
				int len =0;
				while(-1!=(len=bis.read(flush))){						
					bos.write(flush, 0, len);
				}
				bos.flush();
				FileUtil.close(bis);
			}
		} catch (Exception e) {
		}finally{
			FileUtil.close(bos);
		}		
		
	}

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		//SplitFile split = new SplitFile("E:/xp/20130502/test/学员设置(20130502).xls","E:/xp/20130502",51);
		SplitFile split = new SplitFile("D:/father/Hadoop云计算技术介绍.pdf","D:/father/split",1024);
		//System.out.println(split.size);
		
		split.split();
		// 将切割好的散文件在合并到D:/father/myhadoop.pdf中
		split.merge("D:/father/myhadoop.pdf");
	}

}