zip4j

Language	Java (8+), works on Android
License	Apache 2.0
Repository	github.com/srikanth-lingala/zip4j
Documentation	README, javadoc
Depends on	nothing
Read / write	yes / yes, ZIP64, AES-128/256 and ZipCrypto, stored and DEFLATE, split archives

zip4j does common ZIP tasks in one line: new ZipFile("a.zip").extractAll("out"). Its main feature is encryption: it creates and reads both AES (WinZip AES) and ZipCrypto archives, which the JDK can’t do. It also adds, removes and renames entries in existing archives, creates and merges split archives, reports progress and has its own ZipInputStream / ZipOutputStream with password support.

It supports stored and DEFLATE only, not bzip2, LZMA or Zstandard.

Installation#

Maven:

XML

<dependency>
    <groupId>net.lingala.zip4j</groupId>
    <artifactId>zip4j</artifactId>
    <version>2.11.6</version>
</dependency>

Gradle:

implementation("net.lingala.zip4j:zip4j:2.11.6")

Basic usage: create and extract a ZIP#

Java

import java.io.File;
import java.io.IOException;
import net.lingala.zip4j.ZipFile;

public class Example {
    public static void main(String[] args) throws IOException {
        try (ZipFile zip = new ZipFile("out.zip")) {
            zip.addFile(new File("notes.txt"));
            zip.addFolder(new File("photos"));  // adds photos/ recursively
        }

        try (ZipFile zip = new ZipFile("out.zip")) {
            zip.extractAll("extracted");
        }
    }
}

ZipFile operations throw net.lingala.zip4j.exception.ZipException, a subclass of IOException.

How to create a password-protected ZIP with AES#

Java

import java.io.File;
import java.util.List;
import net.lingala.zip4j.ZipFile;
import net.lingala.zip4j.model.ZipParameters;
import net.lingala.zip4j.model.enums.AesKeyStrength;
import net.lingala.zip4j.model.enums.EncryptionMethod;

ZipParameters params = new ZipParameters();
params.setEncryptFiles(true);
params.setEncryptionMethod(EncryptionMethod.AES);  // or ZIP_STANDARD (ZipCrypto, weak)
params.setAesKeyStrength(AesKeyStrength.KEY_STRENGTH_256);

try (ZipFile zip = new ZipFile("secret.zip", "my password".toCharArray())) {
    zip.addFiles(List.of(new File("a.pdf"), new File("b.pdf")), params);
}

How to extract a password-protected ZIP#

Java

try (ZipFile zip = new ZipFile("secret.zip")) {
    if (zip.isEncrypted()) {
        zip.setPassword("my password".toCharArray());
    }
    zip.extractAll("out");
}

How to list files and extract one#

Java

import net.lingala.zip4j.ZipFile;
import net.lingala.zip4j.model.FileHeader;

try (ZipFile zip = new ZipFile("in.zip")) {
    for (FileHeader h : zip.getFileHeaders()) {
        System.out.printf("%-40s %10d -> %10d%s%n", h.getFileName(),
            h.getUncompressedSize(), h.getCompressedSize(), h.isEncrypted() ? " (encrypted)" : "");
    }
    zip.extractFile("docs/readme.txt", "out");  // keeps the docs/ folder
    zip.removeFile("old.log");                   // modifies the archive
}

How to set the compression level#

Java

import net.lingala.zip4j.model.enums.CompressionLevel;
import net.lingala.zip4j.model.enums.CompressionMethod;

ZipParameters params = new ZipParameters();
params.setCompressionMethod(CompressionMethod.DEFLATE);  // or STORE
params.setCompressionLevel(CompressionLevel.MAXIMUM);    // FASTEST, FAST, NORMAL, MAXIMUM
zip.addFolder(new File("docs"), params);

Tips#

zip.createSplitZipFile(files, params, true, 10485760) writes 10 MB parts; mergeSplitFiles joins them into one archive.
zip.setRunInThread(true) plus zip.getProgressMonitor() runs long operations in the background with progress.
zip.setCharset(Charset.forName("Cp437")) reads names from old archives without the UTF-8 flag.
zip4j validates extraction paths and refuses entries that would be written outside the target folder.