package org.kodejava.util.zip;
import java.io.*;
import java.util.zip.ZipInputStream;
import java.util.zip.ZipEntry;
import java.util.zip.CheckedInputStream;
import java.util.zip.Adler32;
public class UnzipWithChecksum {
public static void main(String[] args) throws Exception {
String zipName = "data-1.zip";
try (FileInputStream fis = new FileInputStream(zipName);
// Creating input stream that also maintains the checksum of
// the data which later can be used to validate data
// integrity.
CheckedInputStream checksum =
new CheckedInputStream(fis, new Adler32());
ZipInputStream zis =
new ZipInputStream(new BufferedInputStream(checksum))) {
ZipEntry entry;
// Read each entry from the ZipInputStream until no more entry
// found indicated by a null return value of the getNextEntry()
// method.
while ((entry = zis.getNextEntry()) != null) {
System.out.println("Unzipping: " + entry.getName());
int size;
byte[] buffer = new byte[1048];
try (FileOutputStream fos =
new FileOutputStream(entry.getName());
BufferedOutputStream bos =
new BufferedOutputStream(fos, buffer.length)) {
while ((size = zis.read(buffer, 0, buffer.length)) != -1) {
bos.write(buffer, 0, size);
}
bos.flush();
}
}
// Print out the checksum value
long value = checksum.getChecksum().getValue();
System.out.println("Checksum = " + value);
}
}
}
Category Archives: Zip and GZIP
How do I create checksum for a zip file?
This example demonstrate how to use CheckedOutputStream for creating a checksum of a zip file. Checksum can be used to detect whether a data was corrupted during a transmission process to a remote machine.
package org.kodejava.util.zip;
import java.io.*;
import java.util.Objects;
import java.util.zip.ZipEntry;
import java.util.zip.ZipOutputStream;
import java.util.zip.CheckedOutputStream;
import java.util.zip.Adler32;
public class ZipWithChecksum {
public static void main(String[] args) throws Exception {
String target = "data-1.zip";
try (FileOutputStream fos = new FileOutputStream(target);
// An output stream that also maintains a checksum of the data
// being written. The checksum can then be used to verify the
// integrity of the output data.
CheckedOutputStream checksum =
new CheckedOutputStream(fos, new Adler32())) {
try (ZipOutputStream zos =
new ZipOutputStream(new BufferedOutputStream(checksum))) {
int size;
byte[] buffer = new byte[1024];
// Get all text files on the working folder.
File dir = new File(".");
String[] files = dir.list((directory, name) -> name.endsWith(".txt"));
for (String file : Objects.requireNonNull(files)) {
System.out.println("Compressing: " + file);
try (FileInputStream fis = new FileInputStream(file);
BufferedInputStream bis =
new BufferedInputStream(fis, buffer.length)) {
// put a new ZipEntry in the ZipOutputStream
ZipEntry zipEntry = new ZipEntry(file);
zos.putNextEntry(zipEntry);
// read data to the end of the source file and write it
// to the zip output stream.
while ((size = bis.read(buffer, 0, buffer.length)) > 0) {
zos.write(buffer, 0, size);
}
zos.closeEntry();
}
}
}
// Print out checksum value
long value = checksum.getChecksum().getValue();
System.out.println("Checksum : " + value);
}
}
}
How do I decompress a zip file using ZipFile class?
In this example we use the java.util.zip.ZipFile class to decompress and extract a zip file.
package org.kodejava.util.zip;
import java.util.zip.ZipFile;
import java.util.zip.ZipEntry;
import java.util.Enumeration;
import java.io.*;
public class ZipFileUnzipDemo {
public static void main(String[] args) throws Exception {
String zipName = "data.zip";
ZipFile zip = new ZipFile(zipName);
Enumeration<? extends ZipEntry> enumeration = zip.entries();
while (enumeration.hasMoreElements()) {
ZipEntry zipEntry = enumeration.nextElement();
System.out.println("Unzipping: " + zipEntry.getName());
int size;
byte[] buffer = new byte[2048];
try (BufferedInputStream bis =
new BufferedInputStream(zip.getInputStream(zipEntry));
FileOutputStream fos =
new FileOutputStream(zipEntry.getName());
BufferedOutputStream bos =
new BufferedOutputStream(fos, buffer.length)) {
while ((size = bis.read(buffer, 0, buffer.length)) != -1) {
bos.write(buffer, 0, size);
}
bos.flush();
}
}
}
}
How do I decompress a zip file using ZipInputStream?
The code below shows how to decompress and extract files from a zip archive. In the example we use the java.util.zip.ZipInputStream class.
package org.kodejava.util.zip;
import java.io.*;
import java.util.zip.ZipInputStream;
import java.util.zip.ZipEntry;
public class UnzipDemo {
public static void main(String[] args) {
String zipName = "data.zip";
try (FileInputStream fis = new FileInputStream(zipName);
ZipInputStream zis =
new ZipInputStream(new BufferedInputStream(fis))) {
ZipEntry entry;
// Read each entry from the ZipInputStream until no
// more entry found indicated by a null return value
// of the getNextEntry() method.
while ((entry = zis.getNextEntry()) != null) {
System.out.println("Unzipping: " + entry.getName());
int size;
byte[] buffer = new byte[2048];
try (FileOutputStream fos =
new FileOutputStream(entry.getName());
BufferedOutputStream bos =
new BufferedOutputStream(fos, buffer.length)) {
while ((size = zis.read(buffer, 0, buffer.length)) != -1) {
bos.write(buffer, 0, size);
}
bos.flush();
}
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
How do I create a zip file?
package org.kodejava.util.zip;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.zip.ZipEntry;
import java.util.zip.ZipOutputStream;
public class ZippingFileExample {
public static void main(String[] args) {
String source = "data.txt";
String target = "data.zip";
try (ZipOutputStream zos =
new ZipOutputStream(new FileOutputStream(target));
InputStream is =
ZippingFileExample.class.getResourceAsStream("/" + source)) {
if (is != null) {
// Put a new ZipEntry in the ZipOutputStream
zos.putNextEntry(new ZipEntry(source));
int size;
byte[] buffer = new byte[1024];
// Read data to the end of the source file and write it
// to the zip output stream.
while ((size = is.read(buffer, 0, buffer.length)) > 0) {
zos.write(buffer, 0, size);
}
zos.closeEntry();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}