FileUtil

package test;

import java.io.BufferedInputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FilenameFilter;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

public class FileUtil {

	private final static short MAGIC = (short) 0xacef;
	private final static String SUFFIX = ".part";
	
	public static void main(String[] args) throws IOException {
		FileUtil util = new FileUtil();
//		util.splitBySize("E:\\test\\Spring源码深度解析.pdf", 50 * 1024 * 1024);
		util.mergePartFiles("E:\\test", "E:\\test\\Spring.pdf");
	}
    /**
     * 左填充
     */
    public static String leftPad(String str, int length, char ch) {
        if (str.length() >= length) {
            return str;
        }
        char[] chs = new char[length];
        Arrays.fill(chs, ch);
        char[] src = str.toCharArray();
        System.arraycopy(src, 0, chs, length - src.length, src.length);
        return new String(chs);
    }

    /**
     * 删除文件
     */
    public static boolean delete(String fileName) {
        boolean result = false;
        File f = new File(fileName);
        if (f.exists()) {
            result = f.delete();
        } else {
            result = true;
        }
        return result;
    }

    /***
     * 递归获取指定目录下的所有的文件（不包括文件夹）
     */
    public static List getAllFiles(String dirPath) {
        File dir = new File(dirPath);
        List files = new ArrayList();
        if (dir.isDirectory()) {
            File[] fileArr = dir.listFiles();
            for (int i = 0; i < fileArr.length; i++) {
                File f = fileArr[i];
                if (f.isFile()) {
                    files.add(f);
                } else {
                    files.addAll(getAllFiles(f.getPath()));
                }
            }
        }
        return files;
    }

    /**
     * 获取指定目录下的所有文件(不包括子文件夹)
     */
    public static List getDirFiles(String dirPath) {
        File path = new File(dirPath);
        File[] fileArr = path.listFiles();
        List files = new ArrayList();

        for (File f : fileArr) {
            if (f.isFile()) {
                files.add(f);
            }
        }
        return files;
    }

    /**
     * 获取指定目录下特定文件后缀名的文件列表(不包括子文件夹)
     */
    public static List getDirFiles(String dirPath, final String suffix) {
        File path = new File(dirPath);
        File[] fileArr = path.listFiles(new FilenameFilter() {
            public boolean accept(File dir, String name) {
                String lowerName = name.toLowerCase();
                String lowerSuffix = suffix.toLowerCase();
                if (lowerName.endsWith(lowerSuffix)) {
                    return true;
                }
                return false;
            }
        });
        List files = new ArrayList();
        for (File f : fileArr) {
            if (f.isFile()) {
                files.add(f);
            }
        }
        return files;
    }

    /**
     * 追加内容到指定文件
     */
    public static void append(String fileName, String fileContent) throws IOException {
        File f = new File(fileName);
        if (f.exists()) {
            RandomAccessFile rFile = new RandomAccessFile(f, "rw");
            byte[] b = fileContent.getBytes();
            long originLen = f.length();
            rFile.setLength(originLen + b.length);
            rFile.seek(originLen);
            rFile.write(b);
            rFile.close();
        }
    }

    /**
     * 拆分文件
     */
    public List splitBySize(String fileName, int byteSize) throws IOException {
        List parts = new ArrayList();
        File file = new File(fileName);
        int count = (int) Math.ceil(file.length() / (double) byteSize);
        ThreadPoolExecutor threadPool = new ThreadPoolExecutor(
        		0, count, 1, TimeUnit.SECONDS,
                new ArrayBlockingQueue(count));

        String destDir = file.getParent();
        for (int i = 0; i < count; i++) {
            String partFileName = destDir + File.separator + file.getName()
                    + leftPad(String.valueOf(i + 1), String.valueOf(count).length(), '0') + SUFFIX;
            Fragment f = new Fragment();
            f.count = count;
            f.order = i + 1;
            f.byteSize = byteSize;
            f.startPos = i * byteSize;
            f.partFile = new File(partFileName);
            threadPool.execute(new SplitRunnable(file, f));
            parts.add(partFileName);
        }
        return parts;
    }

    /**
     * 合并文件
     */
    public void mergePartFiles(String dirPath, String mergeFileName) throws IOException {
    	List fragments = collectPartFiles(dirPath);
    	if(fragments.size() < 1){
    		return;
    	}
        RandomAccessFile randomAccessFile = new RandomAccessFile(mergeFileName, "rw");
        Fragment f = fragments.get(fragments.size() -1);
        randomAccessFile.setLength(f.startPos + f.byteSize);
        randomAccessFile.close();

        ThreadPoolExecutor threadPool = new ThreadPoolExecutor(
                0, fragments.size(), 1, TimeUnit.SECONDS,
                new ArrayBlockingQueue(fragments.size()));

        for (int i = 0; i < fragments.size(); i++) {
            threadPool.execute(new MergeRunnable(mergeFileName, fragments.get(i)));
        }
    }
    
    public List collectPartFiles(String dirPath) throws IOException{
    	List partFiles = getDirFiles(dirPath);
    	Set fragments = new HashSet();
    	for(File file : partFiles){
    		DataInputStream in = new DataInputStream(new FileInputStream(file));
    		if(in.available() < 14) continue;
    		short magic = in.readShort();
    		if(magic != MAGIC) continue;
    		int count = in.readInt();
    		int order = in.readInt();
    		int size = in.readInt();
    		if(size + 14 != file.length()) continue;
    		Fragment fragment = new Fragment();
    		fragment.byteSize = size;
    		fragment.count = count;
    		fragment.order = order;
    		fragment.partFile = file;
    		fragments.add(fragment);
    		in.close();
    	}
    	List list = new ArrayList();
    	list.addAll(fragments);
    	Collections.sort(list, new Comparator(){
			@Override
			public int compare(Fragment o1, Fragment o2) {
				return o1.order - o2.order;
			}
    	});
    	long startPos = 0;
    	for(int i = 0; i < list.size(); i++){
    		Fragment f = list.get(i);
    		if(f.order != i + 1){
    			return Collections.emptyList();
    		}
    		if(f.count != list.size()){
    			return Collections.emptyList();
    		}
    		f.startPos = startPos;
    		startPos = startPos + f.byteSize;
    	}
    	return list;
    }

    public static class Fragment {
    	private int count;
    	private int order;
    	private long startPos;
    	private int byteSize;
    	private File partFile;
    	
		public int getCount() {
			return count;
		}
		public void setCount(int count) {
			this.count = count;
		}
		public int getOrder() {
			return order;
		}
		public void setOrder(int order) {
			this.order = order;
		}
		public long getStartPos() {
			return startPos;
		}
		public void setStartPos(long startPos) {
			this.startPos = startPos;
		}
		public int getByteSize() {
			return byteSize;
		}
		public void setByteSize(int byteSize) {
			this.byteSize = byteSize;
		}
		public File getPartFile() {
			return partFile;
		}
		public void setPartFile(File partFile) {
			this.partFile = partFile;
		}
		@Override
		public int hashCode() {
			final int prime = 31;
			long result = 1;
			result = prime * result + byteSize;
			result = prime * result + count;
			result = prime * result + order;
			result = prime * result + startPos;
			return (int)result;
		}
		@Override
		public boolean equals(Object obj) {
			if (this == obj)
				return true;
			if (obj == null)
				return false;
			if (getClass() != obj.getClass())
				return false;
			Fragment other = (Fragment) obj;
			if (byteSize != other.byteSize)
				return false;
			if (count != other.count)
				return false;
			if (order != other.order)
				return false;
			if (startPos != other.startPos)
				return false;
			return true;
		}
		
    }
    
    /**
     * 分割处理Runnable
     */
    private class SplitRunnable implements Runnable {
        File originFile;
        Fragment fragment;

        public SplitRunnable(File originFile, Fragment fragment) {
            this.fragment = fragment;
            this.originFile = originFile;
        }

        public void run() {
            RandomAccessFile rFile;
            DataOutputStream os;
            try {
                rFile = new RandomAccessFile(originFile, "r");
                byte[] b = new byte[fragment.byteSize];
                os = new DataOutputStream(new FileOutputStream(fragment.partFile));
                os.writeShort(MAGIC);
                os.writeInt(fragment.count);
                os.writeInt(fragment.order);
                rFile.seek(fragment.startPos);
                int s = rFile.read(b);
                os.writeInt(s);
                os.write(b, 0, s);
                os.flush();
                os.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    /**
     * 合并处理Runnable
     */
    private class MergeRunnable implements Runnable {
        String mergeFileName;
        Fragment fragment;

        public MergeRunnable(String mergeFileName, Fragment fragment) {
            this.mergeFileName = mergeFileName;
            this.fragment = fragment;
        }

        public void run() {
            RandomAccessFile rFile;
            try {
                rFile = new RandomAccessFile(mergeFileName, "rw");
                rFile.seek(fragment.startPos);
                BufferedInputStream bis = new BufferedInputStream(new FileInputStream(fragment.partFile));
                byte[] buf = new byte[2048];
                bis.read(buf, 0, 14);
                int len = 0;
                while((len = bis.read(buf)) > 0){
                	rFile.write(buf, 0, len);
                }
                bis.close();
                rFile.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}