Código: Seleccionar todo

import java.io.FileOutputStream;
import java.io.IOException;
import java.util.jar.JarEntry;
import java.util.jar.JarOutputStream;

/**
 *
 * @author adwind
 */
public class TestJar {
    
    
    public TestJar(){
        JarOutputStream out=null;
        try {
            out = new JarOutputStream(new FileOutputStream("dinamic.jar"));
            out.putNextEntry(new JarEntry("nota.txt"));
            out.write("Este es un elemento".getBytes());
            out.closeEntry();
            
            out.putNextEntry(new JarEntry("nota2.txt"));
            out.write("Este es un segundo elemento".getBytes());
            out.closeEntry();
            
        } catch (Exception ex) {
ex.printStackTrace();
        } finally {
            try {
                out.close();
            } catch (IOException ex) {

            }
        }
    }
    public static void main(String [] args){
    new TestJar();
    
    }
}