ClassLoader

getClass().getClassLoader().loadClass("cz.softeu.Trida").newInstance();

class MyClassLoader extends ClassLoader {
    public MyClassLoader(ClassLoader parent) {
        super(parent);
    }

    public Class findClass(String name) {
        byte[] b = XXX;
        return defineClass(name, b, 0, b.length);
    }
}

ClassLoader myCL = new MyClassLoader(getClass().getClassLoader());