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Here you will learn how to unzip a file using java.

Unzipping a File

Lets learn how to unzip a file using java.

The java.util.zip.ZipEntry class is used to represent a zip file entry. The java.util.zip.ZipEntry class

implements java.util.zip.ZipConstants interface. Here we passing the zipped file name to be unzipped

using command line argument .To unzip a file first create an object of byte stream then take the array of

any size as per your convenience (Here we are taking 1000 as the size of byte array ) then create a text

file. First convert the zipped file into the byte array and then write the zipped file into it, Toflush and close

the file call flush() and close() respectively.

If it throws any exception then catch it in try/catch block. We are printing the whole exception using

printStrackTrace() method.

Here is the code of the program :

import java.io.*;

import java.util.zip.*;

public class UnzipExample

{

public static voidmain(String a[])

{

try

{

BufferedOutputStream out = null;

ZipInputStream in = new ZipInputStream

(new BufferedInputStream(new FileInputStream(a[0])));

ZipEntry entry;

while((entry = in.getNextEntry()) != null)

{

int count;

byte data[] = new byte[1000];

out = new BufferedOutputStream(new

FileOutputStream("out.txt"),1000);

while ((count = in.read(data,0,1000)) != -1)

{

out.write(data,0,count);

}

out.flush();out.close();

}

}catch(Exception e)

{

e.printStackTrace();

}

}

}

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Here, you will learn to compress a file. You can compress any file using various standalone applications. These standalone applications are

nothing but the zip tools.

Zipping a File

This example shows how to create a zip file in java. In other words, we will learn how to

compress a file just to take less space. We can compress any file using various standalone

applications. These standalone applications are nothing but the zip (compress or decompress

)tools. Examples of zip tools are Winrar, WinZip etc. It is also possible to zip and unzip the files

from your Java applications. This example shows how we zip a file through a java program.

The java.util.zip.DeflaterOutputStream class is immediate supper class of

java.util.zip.ZipOutputStreamclass. java.util.zip. ZipOutputStream implements

java.util.zip.ZipConstants interface. The class ZipOutStream implements an output stream

filter to write files in the zip file format. This class can be used for both compressed and

uncompressed files.

The java.io.FilterOutputStream classextends java.io.BufferedOutputStream class and

implements a buffered output stream. We can write a byte steam into a file on the system. The

java.io.FileInputStream class extends java.io.InputStream class. FileInputStream class is

used to obtain input bytes from a file in a file system. The FileInputStream class is used to read

stream of row bytes (such as image data), for reading streams of characters by considering

FileReader class.

putNextEntry(new ZipEntry(filesToZip)):

This is the method of ZipOutputStream class which is used to enter files one by one to be

zipped. This method is used to close previous zip entry if any active and create the next zip

entry by passing the instance of the ZipEntry class which holds the file name to be zipped. In

this example we are going to zip "profile.txt" into "outFile.zip" .To execute this example you first

need to create profile.txt in same directory.

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Here is the code of the program :

import java.io.*;

import java.util.zip.*;

public class ZipFileExample

{

public static voidmain(String a[])

{

try

{

ZipOutputStream out = new ZipOutputStream(new

BufferedOutputStream(new FileOutputStream("outFile.zip")));

byte[] data = new byte[1000];

BufferedInputStream in = new BufferedInputStream

(new FileInputStream("profile.txt"));

int count;

out.putNextEntry(new ZipEntry("outFile.zip"));

while((count = in.read(data,0,1000)) != -1)

{

out.write(data, 0, count);}

in.close();

out.flush();

out.close();

System.out.println("Your file is zipped");

}

catch(Exception e)

{

e.printStackTrace();

}

}

}