Working with ZIP Archives in Java: java.util.zip and Zip4j

Working with ZIP Archives in Java: java.util.zip and Zip4j

Data compression and archiving is one of the key tasks when developing applications in Java. ZIP archives are widely used for packaging files, transferring data over a network, and saving disk space. In this article, we will take a detailed look at two main approaches to working with ZIP archives in Java: the built-in java.util.zip package and the powerful third-party library Zip4j.

Standard java.util.zip Package

Starting with JDK 1.1, Java has the java.util.zip package, which provides basic classes for working with the ZIP format. Main classes:

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• ZipOutputStream — for creating ZIP archives
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• ZipInputStream — for reading ZIP archives
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• ZipEntry — represents an individual entry (file or folder) inside the archive
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• ZipFile — for random access to the contents of the archive
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Creating a ZIP Archive with java.util.zip

import java.io.*;\nimport java.util.zip.*;\n\npublic class ZipCreator {\n    public static void main(String[] args) throws IOException {\n        String sourceFile = "document.txt";\n        String zipName = "archive.zip";\n\n        try (FileOutputStream fos = new FileOutputStream(zipName);\n             ZipOutputStream zos = new ZipOutputStream(fos)) {\n\n            File fileToZip = new File(sourceFile);\n            FileInputStream fis = new FileInputStream(fileToZip);\n\n            ZipEntry zipEntry = new ZipEntry(fileToZip.getName());\n            zos.putNextEntry(zipEntry);\n\n            byte[] buffer = new byte[1024];\n            int length;\n            while ((length = fis.read(buffer)) >= 0) {\n                zos.write(buffer, 0, length);\n            }\n            zos.closeEntry();\n            fis.close();\n        }\n        System.out.println("Archive created: " + zipName);\n    }\n}

Extracting a ZIP Archive

import java.io.*;\nimport java.util.zip.*;\n\npublic class ZipExtractor {\n    public static void main(String[] args) throws IOException {\n        String zipFile = "archive.zip";\n        String outputDir = "extracted";\n\n        new File(outputDir).mkdirs();\n\n        try (ZipInputStream zis = new ZipInputStream(new FileInputStream(zipFile))) {\n            ZipEntry entry;\n            while ((entry = zis.getNextEntry()) != null) {\n                File newFile = new File(outputDir, entry.getName());\n                new File(newFile.getParent()).mkdirs();\n\n                FileOutputStream fos = new FileOutputStream(newFile);\n                byte[] buffer = new byte[1024];\n                int len;\n                while ((len = zis.read(buffer)) > 0) {\n                    fos.write(buffer, 0, len);\n                }\n                fos.close();\n                zis.closeEntry();\n            }\n        }\n        System.out.println("Extraction completed to folder: " + outputDir);\n    }\n}

Limitations of java.util.zip:

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• No encryption support (password protection)
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• Limited Unicode support in file names (before Java 7)
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• No ZIP64 support for archives > 4 GB (before Java 8)
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• Complexity when working with nested folders
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Zip4j Library — Extended Capabilities

Zip4j is a popular open-source third-party library that addresses most of the limitations of the standard package. To use it, add the dependency in Maven:

<dependency>\n    <groupId>net.lingala.zip4j</groupId>\n    <artifactId>zip4j</artifactId>\n    <version>2.11.5</version>\n</dependency>

Creating an Encrypted ZIP Archive with Zip4j

import net.lingala.zip4j.ZipFile;\nimport net.lingala.zip4j.model.ZipParam