Esempio di metodo java.util.zip.ZipEntry.setCrc ()

Descrizione

Il java.util.zip.ZipEntry.setCrc(long crc) Il metodo imposta il checksum CRC-32 dei dati di ingresso non compressi.

Dichiarazione

Di seguito è riportata la dichiarazione per java.util.zip.ZipEntry.setCrc(long crc) metodo.

public void setCrc(long crc)

Parametri

IllegalArgumentException - se il valore CRC-32 specificato è minore di 0 o maggiore di 0xFFFFFFFF.

Eccezioni

crc - il valore CRC-32.

Pre-requisito

Crea un file Hello.txt in formato D:> test > directory con il seguente contenuto.

This is an example.

Esempio

L'esempio seguente mostra l'utilizzo del metodo java.util.zip.ZipEntry.setCrc (long crc).

package com.tutorialspoint;

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.CRC32;
import java.util.zip.ZipEntry;
import java.util.zip.ZipFile;
import java.util.zip.ZipOutputStream;

public class ZipEntryDemo {
   private static String SOURCE_FILE = "D:\\test\\Hello.txt";
   private static String TARGET_FILE = "D:\\test\\Hello.zip";

   public static void main(String[] args) {
      try {
         createZipFile();
         readZipFile();
      } catch(IOException ioe) {
         System.out.println("IOException : " + ioe);
      }
   }

   private static void createZipFile() throws IOException{
      FileOutputStream fout = new FileOutputStream(TARGET_FILE);
      ZipOutputStream zout = new ZipOutputStream(fout);

      FileInputStream fin = new FileInputStream(SOURCE_FILE);
      byte[] buffer = new byte[1024];
      fin.read(buffer, 0, buffer.length);
      
      ZipEntry zipEntry = new ZipEntry(SOURCE_FILE);      
      CRC32 crc = new CRC32();
      zipEntry.setSize((long) buffer.length);
      crc.reset();
      crc.update(buffer);
      zipEntry.setCrc(crc.getValue());
      zipEntry.setTime(System.currentTimeMillis());
      zout.putNextEntry(zipEntry);
      
      zout.write(buffer, 0, buffer.length);

      zout.closeEntry();
      fin.close();
      zout.close();
   }

   private static void readZipFile() throws IOException{
      final ZipFile file = new ZipFile(TARGET_FILE); 
      System.out.println("Iterating over zip file : " + TARGET_FILE);
      try { 
         final Enumeration<? extends ZipEntry> entries = file.entries(); 
         while (entries.hasMoreElements()) { 
            final ZipEntry entry = entries.nextElement(); 
            System.out.printf("File: %s Size %d Modified on %TD %n", 
               entry.getName(), entry.getSize(), 
                  new Date(entry.getTime())); 
            extractFile(entry, file.getInputStream(entry)); 
         } 
         System.out.printf("Zip file %s extracted successfully.", SOURCE_FILE); 
      } 
      finally { 
         file.close(); 
      }
   }

   private static void extractFile(final ZipEntry entry, InputStream is) 
      throws IOException {
      FileOutputStream fos = null; 
      try { 
         fos = new FileOutputStream(entry.getName()); 
         final byte[] buf = new byte[1024]; 
         int read = 0; 
         int length; 
         while ((length = is.read(buf, 0, buf.length)) >= 0) { 
            fos.write(buf, 0, length); 
         } 
      } catch (IOException ioex) { 
         fos.close(); 
      } 
   }
}

Compiliamo ed eseguiamo il programma sopra, questo produrrà il seguente risultato:

Iterating over zip file : D:\test\Hello.zip
File: D:\test\Hello.txt Size 1024 Modified on 05/20/17 
Zip file D:\test\Hello.txt extracted successfully.

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