Geeting error when reflecting .class file from jar file which .class file is extending or implementing other class which class is present in dependenc

I have a jar file which contains only testcase.class files. I need to parse that and find all the classes defined in that jar file and need to generate one report. I tried to do it with the reflection concept in Java. Some how, when loading a class is fine, but trying to get the declared methods of it, I am getting the following error. (Note class is loaded, I am able to get the name and canonical name of the loaded class but I error at trying to get declared methods).

for (String clazz: classes) {  
            String className = clazz.replaceAll("/",  
 ".").replaceAll(".class","");  
            try {  
                URL url = file.toURI().toURL();  
                URL[] urls = new URL[]{url};  
                URLClassLoader cl = new URLClassLoader(urls);  
                Class cls = cl.loadClass(className);  
                System.out.println("##############################");  
                cls.getDeclaredMethods();
                //clazzes.add(getClassObject(cls));  
                //break;  
            } catch (MalformedURLException e) {  
                e.printStackTrace();  
            } catch (ClassNotFoundException e) {  
                e.printStackTrace();  
            }  
        }  



Exception in thread "main" java.lang.NoClassDefFoundError: javax/mail/Authenticator
    at java.base/java.lang.ClassLoader.defineClass1(Native Method)
    at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:1016)
    at java.base/java.security.SecureClassLoader.defineClass(SecureClassLoader.java:174)
    at java.base/java.net.URLClassLoader.defineClass(URLClassLoader.java:555)
    at java.base/java.net.URLClassLoader$1.run(URLClassLoader.java:458)
    at java.base/java.net.URLClassLoader$1.run(URLClassLoader.java:452)
    at java.base/java.security.AccessController.doPrivileged(Native Method)
    at java.base/java.net.URLClassLoader.findClass(URLClassLoader.java:451)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:588)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521)
    at com.springboot.example.springBootExample.service.JarParserService.getTypes(JarParserService.java:99)
    at com.springboot.example.springBootExample.service.JarParserService.constructPackages(JarParserService.java:86)
    at com.springboot.example.springBootExample.service.JarParserService.getClassTypes(JarParserService.java:78)
    at com.springboot.example.springBootExample.service.JarParserService.scanJar(JarParserService.java:61)
    at com.springboot.example.springBootExample.service.JarParserService.getAllPackages(JarParserService.java:34)
    at com.springboot.example.springBootExample.service.FindClassesFromJarService.parseJar(FindClassesFromJarService.java:61)
    at com.springboot.example.springBootExample.service.FindClassesFromJarService.main(FindClassesFromJarService.java:31)
Caused by: java.lang.ClassNotFoundException: javax.mail.Authenticator
    at java.base/java.net.URLClassLoader.findClass(URLClassLoader.java:476)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:588)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521)
    ... 17 more

Process finished with exit code 1