2 Examples To Read Null Files Inwards Java, Zipfile Vs Zipinputstream

ZIP format is 1 of the most pop compression machinery inwards figurer world. H5N1 Zip file may contains multiples files or folder inwards compressed format.  Java API provides extensive back upwards to read Zip files, all classes related to zip file processing are located inwards java.util.zip package. One of the  most mutual chore related to zip archive is to read a Zip file together with display what entries it contains, together with hence extract them inwards a folder. In this tutorial nosotros volition acquire how to do this chore inwards Java. There are 2 ways you lot tin iterate over all items inwards a given zip archive, you lot tin role either java.util.zip.ZipFile or java.util.zip.ZipInputStream. Since a Zip file contains several items, each of them has header plain containing size of items inwards discover of bytes. Which agency you lot tin iterate all entries without genuinely decompressing the zip file.

The ZipFile class accepts a java.io.File or String file name, it opens a ZIP file for reading together with UTF-8 charset is used to decode the entry names together with comments.

Main do goodness of using ZipFile over ZipInputStream is that it uses random access to iterate over dissimilar entries, acre ZipInputStream is sequential, because it industrial plant  with stream, due to which it's non able to motion positions freely.

It has to read together with decompress all zip information inwards enterprise to achieve EOF for each entry together with read header of adjacent entry. That's why its ameliorate to role ZipFile class over ZipInputStream for iterating over all entries from archive.

We volition acquire to a greater extent than virtually how to role read Zip file inwards Java, yesteryear next an example. By the way, code should operate with zip file created yesteryear whatever zip utility e.g. WinZip, WinRAR or whatever other tool, .ZIP format permits multiple compression algorithms.. I guide keep tested alongside Winzip inwards Windows 8, only it should operate alongside zip file created yesteryear whatever tool.

Reading Zip archive inwards Java

In this example, I guide keep used ZipFile class to iterate over each file from Zip archive. getEntry() method of ZipFile returns an entry, which has all meta information including name, size together with modified appointment together with time.

You tin inquire ZipFile for InputStream corresponding to this file entry for extracting existent data. Which means, you lot solely incur terms of decompression, when you lot genuinely take away to. By using java.util.zip.ZipFile, you lot tin banking enterprise check each of entry together with solely extract sure as shooting entries, depending upon your logic.

ZipFile is skillful for both sequential together with random access of private file entries. On the other hand, if you lot are using ZipInptStream hence similar any other InputStream, you lot volition take away to procedure all entries sequentially, every bit shown inwards 2d example.

Key betoken to remember, peculiarly if you lot are processing large zip archives is that, Java vi solely back upwards zip file upwards to 2GB. Thankfully Java vii supports zip64 mode, which tin live used to procedure large zip file alongside size to a greater extent than than 2GB.

import java.io.BufferedInputStream; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.util.Date; import java.util.Enumeration; import java.util.zip.ZipEntry; import java.util.zip.ZipFile; import java.util.zip.ZipInputStream;  /**  * Java plan to iterate together with read file entries from Zip archive.  * This plan demonstrate 2 ways to retrieve files from Zip using ZipFile together with yesteryear using ZipInputStream class.  * @author Javin  */  public class ZipFileReader {      // This Zip file contains eleven PNG images     private static lastly String FILE_NAME = "C:\\temp\\pics.zip";     private static lastly String OUTPUT_DIR = "C:\\temp\\Images\\";     private static lastly int BUFFER_SIZE = 8192;      public static void main(String args[]) throws IOException {          // Prefer ZipFile over ZipInputStream         readUsingZipFile();     //  readUsingZipInputStream();      }      /*      * Example of reading Zip archive using ZipFile course of pedagogy      */      private static void readUsingZipFile() throws IOException {         lastly ZipFile file = new ZipFile(FILE_NAME);         System.out.println("Iterating over zip file : " + FILE_NAME);          try {             lastly Enumeration<? extends ZipEntry> entries = file.entries();             while (entries.hasMoreElements()) {                 lastly ZipEntry entry = entries.nextElement();                 System.out.printf("File: %s Size %d  Modified on %TD %n", entry.getName(), entry.getSize(), new Date(entry.getTime()));                 extractEntry(entry, file.getInputStream(entry));             }             System.out.printf("Zip file %s extracted successfully inwards %s", FILE_NAME, OUTPUT_DIR);         } finally {             file.close();         }      }      /*      * Example of reading Zip file using ZipInputStream inwards Java.      */      private static void readUsingZipInputStream() throws IOException {         BufferedInputStream bis = new BufferedInputStream(new FileInputStream(FILE_NAME));         lastly ZipInputStream is = new ZipInputStream(bis);          try {             ZipEntry entry;             while ((entry = is.getNextEntry()) != null) {                 System.out.printf("File: %s Size %d  Modified on %TD %n", entry.getName(), entry.getSize(), new Date(entry.getTime()));                 extractEntry(entry, is);             }         } finally {             is.close();         }      }      /*      * Utility method to read  information from InputStream      */      private static void extractEntry(final ZipEntry entry, InputStream is) throws IOException {         String exractedFile = OUTPUT_DIR + entry.getName();         FileOutputStream fos = null;          try {             fos = new FileOutputStream(exractedFile);             lastly byte[] buf = new byte[BUFFER_SIZE];             int read = 0;             int length;              while ((length = is.read(buf, 0, buf.length)) >= 0) {                 fos.write(buf, 0, length);             }          } catch (IOException ioex) {             fos.close();         }      }  }  Output: Iterating over zip file : C:\temp\pics.zip File: Image  (11).png Size 21294  Modified on 10/24/13 File: Image  (1).png Size 22296  Modified on 11/19/13 File: Image  (2).png Size 10458  Modified on 10/24/13 File: Image  (3).png Size 18425  Modified on 11/19/13 File: Image  (4).png Size 31888  Modified on 11/19/13 File: Image  (5).png Size 27454  Modified on 11/19/13 File: Image  (6).png Size 67608  Modified on 11/19/13 File: Image  (7).png Size 8659  Modified on 11/19/13 File: Image  (8).png Size 40015  Modified on 11/19/13 File: Image  (9).png Size 17062  Modified on 10/24/13 File: Image  (10).png Size 42467  Modified on 10/24/13 Zip file C:\temp\pics.zip extracted successfully in C:\temp\Images\

In enterprise to run this file, brand your you lot must have, zip file alongside mention pics.zip inwards C:\temp, together with output directory C:\temp\Images available, otherwise it volition throw java.lang.NullPointerException. After successful run of this program, you lot tin run into contents of zip file extracted within output directory. By the way, every bit an exercise, you lot tin enhance this plan to acquire mention of zip file from user together with do output directory of same name.

That's all virtually How to read Zip file inwards Java. We guide keep seen 2 dissimilar approaches to iterate over each file entries inwards Zip file together with retrieve them. You should prefer using ZipFile over ZipInputStream for iterating over each file from archive. It's also skillful to know that java.uti.zip parcel also back upwards GZIP file formats, which agency you lot tin also read .gz files generated yesteryear gzip command inwards UNIX from your Java program.

Further Learning
Complete Java Masterclass
Java Fundamentals: The Java Language
Java In-Depth: Become a Complete Java Engineer!

Bagikan Artikel ini