Java Verify Zip File
ZIP format is one of the most popular compression mechanism in computer world. A Zip file may contains multiples files or folder in compressed format. Java API provides extensive support to read Zip files, all classes related to zip file processing are located in java.util.zip package. One of the most common task related to zip archive is to read a Zip file and display what entries it contains, and then extract them in a folder. In this tutorial we will learn how to do this task in Java.
Compressing and Decompressing Data Using Java. Decompressing and Extracting Data from a ZIP file. Using the checksum you can check whether the file. Zip a Directory In Java. Through its java.util.zip package. Note that the following method does not add an empty directory to the produced ZIP file.
There are two ways you can over all items in a given zip archive, you can use either java.util.zip.ZipFile or java.util.zip.ZipInputStream. Since a Zip file contains several items, each of them has header field containing size of items in number of bytes. Which means you can iterate all entries without actually decompressing the zip file. The ZipFile class accepts a java.io.File or String file name, it opens a ZIP file for reading and is used to decode the entry names and comments. Main benefit of using ZipFile over ZipInputStream is that it uses random access to iterate over different entries, while ZipInputStream is sequential, because it works with stream, due to which it's not able to move positions freely.
It has to read and decompress all zip data in order to reach EOF for each entry and read header of next entry. That's why its better to use ZipFile class over ZipInputStream for iterating over all entries from archive. We will learn more about how to use read Zip file in Java, by following an example. By the way, code should work with created by any zip utility e.g.
WinZip, WinRAR or any other tool,.ZIP format permits multiple compression algorithms. I have tested with Winzip in Windows 8, but it should work with zip file created by any tool. Reading Zip archive in Java In this example, I have used ZipFile class to iterate over each file from Zip archive.
GetEntry method of ZipFile returns an entry, which has all meta data including name, size and modified date and time. You can ask ZipFile for corresponding to this file entry for extracting real data. Which means, you only incur cost of decompression, when you really need to. By using java.util.zip.ZipFile, you can check each of entry and only extract certain entries, depending upon your logic. ZipFile is good for both sequential and random access of individual file entries.
On the other hand, if you are using ZipInptStream then like, you will need to process all entries sequentially, as shown in second example. Key point to remember, especially if you are processing large zip archives is that, Java 6 only support zip file up to 2GB.
Thankfully Java 7 supports zip64 mode, which can be used to process large zip file with size more than 2GB. Can we also compress more than one text files with help of this API? Nice article, but last words are - 'It's also good to know that java.uti.zip package'. Some missprint here in package name Anonymous said. @Of al., yes you can compre more than one text files using tihs API. It allows you to create a ZIP file from a directory, which may contain sub-directories. You can even ues WinZip, WinRAR and 7-Zip to open Zip files created in Java.
In UNIX, you can use zip command by it's own or gunzip command. Anonymous said.
@Lanqu is right, there seems to be a little L is missing there, it should be java.util.zip package:-), looks like @Lanqu has got really good observation skills. Anonymous said. I have an issue here, I was trying to create a big zip file to backup lots of images and video files using Java but I am getting java.lang.OutOfMemoryError again? I tried to increase heap space but it didn't help, any idea? Anonymous said.
You can use Zip4j library to easily create zip file, extract a single or all files from zip archive, split them just like Winzip and many more. It's very useful open source library to deal with ZIP file in Java.
I prefer to use this library instead of writing code every time. Anonymous said.
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Can you please provide code for creating zip files inside another zip file said. Hello @Anonymous, zip file is just another, try the same program and just ask it to archive a zip file.