In this Java File IO tutorial, you will learn how to write Java code to read content of a ZIP file without extracting it.

You know, reading content of a ZIP file means that you list all entries contained in the file without extracting them. In the java.util.zip package, the ZipFile class can be used to open and read a ZIP file like this:

ZipFile zipFile = new ZipFile(zipFilePath);
Enumeration<? extends ZipEntry> entries = zipFile.entries();

Each entry is of type ZipEntry which provides the following methods for reading information of an individual entry (to name a few):

• getName(): returns the name of the entry in form of a relative path

• getComment(): returns comment of the entry

• getCompressedSize(): returns the compressed size of the entry in bytes.

• getSize(): returns the normal size (uncompressed) of the entry in bytes.

• isDirectory(): tells whether the entry is a directory or not.

For example, the following program prints the content of a ZIP file whose path is passed from the command line:

import java.io.*;
import java.util.*;
import java.util.zip.*;

/**
 * This program reads contents of a ZIP file.
 *
 * @author www.codejava.net
 */
public class ReadZipFile {

	private static void read(String zipFilePath) {
		try {
			ZipFile zipFile = new ZipFile(zipFilePath);

			Enumeration<? extends ZipEntry> entries = zipFile.entries();

			while (entries.hasMoreElements()) {
				ZipEntry entry = entries.nextElement();
				String name = entry.getName();
				long compressedSize = entry.getCompressedSize();
				long normalSize = entry.getSize();
				String type = entry.isDirectory() ? "DIR" : "FILE";

				System.out.println(name);
				System.out.format("\t %s - %d - %d\n", type, compressedSize, normalSize);
			}

			zipFile.close();
		} catch (IOException ex) {
			System.err.println(ex);
		}
	}


	public static void main(String[] args) {
		String zipFilePath = args[0];
		read(zipFilePath);
	}
}

 Run this program like this:

java ReadZipFile <zip_file_path>

 

For example:

java ReadZipFile exercises_week12.zip

 

This would print the following output:

exercise1/

         DIR - 0 - 0

exercise1/Book.class

         FILE - 868 - 1906

exercise1/Book.java

         FILE - 442 - 1689

exercise1/Book.java~

         FILE - 258 - 1066

exercise1/Main.class

         FILE - 1631 - 3159

exercise1/Main.java

         FILE - 707 - 1964

exercise2/

         DIR - 0 - 0

exercise2/Book.class

         FILE - 868 - 1906

exercise2/Book.java

         FILE - 442 - 1689

exercise2/BookStats.class

         FILE - 2558 - 5748

exercise2/BookStats.java

         FILE - 897 - 3292

As you can see in the output above, the entries in a ZIP file is in the form of a list which includes directories and files. And based on this information, you can write code to decompress a ZIP file properly.

 

API References:

• ZipFile
• ZipEntry
• ZipInputStream

 

Related Java Zip File Tutorials:

• How to compress files in ZIP format in Java
• How to extract a ZIP file in Java
• How to compress directories to ZIP file in Java

 

Other Java File IO Tutorials:

• How to Read and Write Text File in Java
• How to Read and Write Binary Files in Java
• Java IO - Common File and Directory Operations Examples
• Java Serialization Basic Example
• Understanding Java Externalization with Examples
• How to execute Operating System Commands in Java
• 3 ways for reading user's input from console in Java
• File change notification example with Watch Service API
• Java Scanner Tutorial and Code Examples