How do I read a zip file checksum value?

package org.kodejava.example.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);
        }
    }
}

Wayan Saryada

Founder at Kode Java Org
I am a programmer, a runner, a recreational diver, currently live in the island of Bali, Indonesia. Mostly programming in Java, Spring Framework, Hibernate / JPA. You can support my works by donating here. Thank you 🥳

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