Lerning how to get classes && packages from other jars

Main.java

package me.tmp.jar2;

import java.io.FileInputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.zip.ZipEntry;
import java.util.zip.ZipInputStream;

public class Main
{
    public static void main(String[] args)
    {
        List<String> classNames = new ArrayList<String>();
        try {
            ZipInputStream zip = new ZipInputStream(new FileInputStream("C:/Users/kingo/Desktop/jar1.jar"));
            for (ZipEntry entry = zip.getNextEntry(); entry != null; entry = zip.getNextEntry()) {

                if (!entry.isDirectory()) {
                    String className = entry.getName().replace('/', '.');
                    classNames.add(className.substring(0, className.length()));
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        }

        for (String s : classNames) {
            if (s.contains("t2.txt")) {
                System.out.println("Found t2.txt");
            }

            System.out.println(s);
        }
    }
}