Java access Methods from .class files

Question

Hey I'm trying to use javas reflection capabilities to get some info on methods declared in an unknown class file (Decoder.class)

I first placed the Decoder.class file in the root directory of my (eclipse) project workspace.

try {
        File file = new File(".");
        URL url = file.toURL();
        URL[] urls = new URL[] { url };
        ClassLoader cl = new URLClassLoader(urls);
        Class c = cl.loadClass("Decoder");
        System.out.println(c.isInterface());

        printMethods(c);
        printConstructor(c);
    }
    catch (ClassNotFoundException e) {
        System.out.println("Requested class was not found " + e.getMessage());
    }
    catch (MalformedURLException e) {
        System.out.println("Given class file url was not found " + e.getMessage());
    }

that gave me the error

Exception in thread "main" java.lang.NoClassDefFoundError: Decoder (wrong name: ea_6_1/Decoder)

That looks to my that the name of the unkown class within Decoder.class is actually Decoder. However it's declared within the package "ea_6_1")

i then created a subfolder ea_6_1 within the workspace and changed

 Class c = cl.loadClass("Decoder");

to

Class c = cl.loadClass("ea_6_1/Decoder");

but this gives me an illegal name exception.

Exception in thread "main" java.lang.NoClassDefFoundError: IllegalName: ea_6_1/Decoder

So how can i Import a class from another package?

greets:)

Answer 1

使用完全限定的类名Class c = cl.loadClass("com.example.ea_6_1.Decoder");

Answer 2

Try using the fully qualified class name:

try {
    File file = new File(".");
    URL url = file.toURL();
    URL[] urls = new URL[] { url };
    ClassLoader cl = new URLClassLoader(urls);
    Class c = cl.loadClass("design.pattern.Person");
    System.out.println(c.isInterface());
}
catch (Exception e) {
    e.printStackTrace();
}

Answer 3

You need to give the binary name /fully qualified name as specified in the docs .

So instead of using Example you need to use full.package.name.Example