Splitting a zip file and rejoining it

[shirish katti]

Hi all,

I am developing an application into which i need to split a huge zip file into 4 to 5 parts and then rejoin it...

I have tried this with the code i have attached...

The splitting part works perfectly.. Even the re joining part works but the rejoined file is of 0kb with no content into it...

Any of you free then please execute this code snippet and let me know if you have any solution...

Thanks in Advance..

 import java.io.RandomAccessFile;
import java.io.File;

public class Splitter
{
public static void main(String args[])
{
        //Checking the presents of argument.
        if(args.length==0)
        {
                System.out.println("Type -h for getting help on this splitter");
        }
        else if (args.length==1)
        {
                //if the paramenter is -h, the system displays the syntax for using this utility.
                if(args[0].equals("-h"))
                {
                        System.out.println("-----------------------------------");
                        System.out.println("Splitting.....");
                        System.out.println("                  java Splitter -s <filepath> <Split file size in bytes>");
                        System.out.println("-----------------------------------");
                        System.out.println("Joining.....");
                        System.out.println("                  java Splitter -j <filepath>");
                        System.out.println("-----------------------------------");
                }
                // Displaying the error if parameter required are not given.
                else if(args[0].equals("-s") || args[0].equals("-j"))
                {
                        System.out.println("Parameters missing, type -h for help.....");
                }
        }
        //if the parameter is -s then splitting of file happens.
        else if(args[0].equals("-s"))
        {
                if(args.length==3)
                {
                        String FilePath="";
                        FilePath=args[1];
                        File filename=new File(FilePath);
                        int splitFileSize=0;
                        if(filename.exists())
                        {
                                try
                                {
                                        splitFileSize=Integer.parseInt(args[2]);
                                        Splitter spObj=new Splitter();
                                        spObj.split(FilePath,splitFileSize);
                                        spObj=null;
                                }
                                catch(Exception e)
                                {
                                        e.printStackTrace();
                                }
                        }
                        else
                        {
                                System.out.println("File Not Found....");
                        }
                        filename=null;
                        FilePath=null;
                }
                else
                {
                        System.out.println("Parameters missing, type -h for help.....");
                }
        }
        //if the parameter is -s then joining of file happens.
        else if(args[0].equals("-j"))
        {
                String FilePath="";
                FilePath=args[1];
                File filename=new File(FilePath.trim());
                if(filename.exists())
                {
                        FilePath=FilePath.substring(0,FilePath.length()-4);
                        filename=new File(FilePath);
                        if(filename.exists())
                        {
                                System.out.println("\""+ FilePath+ "\" File Already Exist....");
                        }
                        else
                        {
                                Splitter spObj=new Splitter();
                                spObj.join(FilePath);
                                spObj=null;
                        }
                }
                else
                {
                        System.out.println(FilePath+filename);
                        System.out.println("File Not Found....");
                }
                filename=null;
                FilePath=null;
        }
        System.out.println();
        System.out.println();
        
}

public void join(String FilePath)
{
        //long leninfile=0;
        long leng=0;
        int count=1,data=0;
        try
        {
                File filename=new File(FilePath);
                RandomAccessFile outfile = new RandomAccessFile(filename,"rws");
                while(true)
                {
                        //filename=new File(FilePath + count + ".sp");
                        filename=new File(FilePath + count);
                        if (filename.exists())
                        {
                                RandomAccessFile infile = new RandomAccessFile(filename,"r");
                                data=infile.read();
                                while(data!=-1)
                                {
                                        outfile.write(data);
                                        data=infile.read();
                                }
                                leng++;
                                infile.close();
                                count++;
                        }
                        else
                        {
                                break;
                        }
                }
                outfile.close();
                System.out.println("*******File Join Sucessfull*******");
        }
        catch(Exception e)
        {
                e.printStackTrace();
        }
}

public void split(String FilePath,int splitlen)
{
        long leninfile=0,leng=0;
        int count=1,data;
        try
        {
                File filename=new File(FilePath);
                RandomAccessFile infile = new RandomAccessFile(filename,"r");
                data=infile.read();
                while(data!=-1)
                {
                        filename=new File(FilePath + count + ".sp");
                        RandomAccessFile outfile = new RandomAccessFile(filename,"rw");
                        while( data!=-1 && leng<splitlen)
                        {
                                outfile.write(data);
                                leng++;
                                data=infile.read();
                        }
                        leninfile+=leng;
                        leng=0;
                        outfile.close();
                        count++;
                }
                System.out.println("*******File split successfull*******");
                
        }
        catch(Exception e)
        {
                e.printStackTrace();
        }
}
}
   

[Rob Spoor]

Lines 114 and 130 cause your loop to break off immediately. You're join method looks for files without the ".sp" extension. If you use line 111 instead of line 112 the program actually runs.

You may want to consider different ways of reading and writing though. Your split takes 6 seconds for a 801kB file with chunk size of 100kB. Your join of the same chunks then takes 301 seconds!

Instead of using RandomAccessFile, try using FileInputStream and FileOutputStream instead. Here's your join method with streams:

    public void join(String FilePath)
    {
        //long leninfile = 0;
        long leng = 0;
        int count = 1,data = 0;
        try
        {
            File filename = new File(FilePath);
            OutputStream outfile = new FileOutputStream(filename);
//            RandomAccessFile outfile = new RandomAccessFile(filename, "rws");
            while (true)
            {
                filename = new File(FilePath + count + ".sp");
                //filename = new File(FilePath + count);
                if (filename.exists())
                {
                    InputStream infile = new FileInputStream(filename);
                    //RandomAccessFile infile = new RandomAccessFile(filename,
                    //"r");
                    data = infile.read();
                    while (data != -1)
                    {
                        outfile.write(data);
                        data = infile.read();
                    }
                    leng++;
                    infile.close();
                    count++;
                }
                else
                {
                    break;
                }
            }
            outfile.close();
            System.out.println("*******File Join Sucessfull*******");
        }
        catch(Exception e)
        {
            e.printStackTrace();
        }
    }

As you see, I only changed the RandomAccessFile references to use (File)OutputStream and (File)InputStream instead. I've gone down to 6 seconds for the join. You can perhaps even improve it a bit more by using buffering; simply change lines 9 and 17 from my code to these:

OutputStream outfile = new BufferedOutputStream(new FileOutputStream(filename));
// and
InputStream infile = new BufferedInputStream(new FileInputStream(filename));

This is called stream chaining. With this buffering the join method now returns within a second, with the same results. I'm sure that using the same approach for the split method will have similar speed improvements.

[shirish katti]

Hi Rob,

Thanks for your prompt reply...

Thanks for make it time efficient...

Lines 114 and 130 cause your loop to break off immediately. You're join method looks for files without the ".sp" extension. If you use line 111 instead of line 112 the program actually runs.

sorry for this actually i had used line 111 itself...

Even joining is working but the thing is the joined file shows as 0kb and when i use win zip to open it.. It opens and works fine only until i keep the source file i mean the original file in the same location if i delete the source file then it doesn't work properly..

In short it gets redirected to the source file.. Any idea..

[Rob Spoor]

Your output file remains as 0 bytes until your program closes because you never flush() your changes. Once you close the file it gets flushed automatically, and the file will have the proper size. But like I said, my measurements with just a small file already took me 5 minutes to join. I've also shown you how to improve that speed.

[shirish katti]

Hi Rob,

I have even tried it with flushing the file...

As per my knowledge flushing doesn't guarantees that the content is written to the physical disk...

I made this code time efficient, but the problem of output file of 0kb still remains the same..

  public void join(String FilePath)  
     {  
         //long leninfile = 0;  
         long leng = 0;  
         int count = 1,data = 0;  
         try  
         {  
             File filename = new File(FilePath);  
             OutputStream outfile = new BufferedOutputStream(new FileOutputStream(filename));  
             //RandomAccessFile outfile = new RandomAccessFile(filename, "rws");  
             while (true)  
             {  
                 filename = new File(FilePath + count + ".sp");  
                 //filename = new File(FilePath + count);  
                 if (filename.exists())  
                 {  
                     InputStream infile = new BufferedInputStream(new FileInputStream(filename));  
                     //RandomAccessFile infile = new RandomAccessFile(filename,"r");  
                     data = infile.read();  
                     while (data != -1)  
                     {  
                         outfile.write(data);  
                         data = infile.read();  
                     }  
                     leng++;  
                     infile.close();  
                     count++;  
                 }  
                 else  
                 {  
                     break;  
                 }  
             }  
             outfile.flush();
             outfile.close();  
             System.out.println("*******File Join Sucessfull*******");  
         }  
         catch(Exception e)  
         {  
             e.printStackTrace();  
         }  
     }  

public void split(String FilePath,int splitlen)
{
        long leninfile=0,leng=0;
        int count=1,data;
        try
        {
                File filename=new File(FilePath);
                //RandomAccessFile infile = new RandomAccessFile(filename,"r");
                InputStream infile=new BufferedInputStream(new FileInputStream(filename));
                data=infile.read();
                while(data!=-1)
                {
                        filename=new File(FilePath + count + ".sp");
                        //RandomAccessFile outfile = new RandomAccessFile(filename,"rw");
                        OutputStream outfile=new BufferedOutputStream(new FileOutputStream(filename));
                        while( data!=-1 && leng<splitlen)
                        {
                                outfile.write(data);
                                leng++;
                                data=infile.read();
                        }
                        leninfile+=leng;
                        leng=0;
                        outfile.close();
                        count++;
                }
                System.out.println("*******File split successfull*******");
                
        }
        catch(Exception e)
        {
                e.printStackTrace();
        }
}