Yes, something like:

Class<?> clazz = Class.forName(className);
Constructor<?> ctor = clazz.getConstructor(String.class);
Object object = ctor.newInstance(new Object[] { ctorArgument });

That will only work for a single string parameter of course, but you can modify it pretty easily.

Note that the class name has to be a fully-qualified one, i.e. including the namespace. For nested classes, you need to use a dollar (as that's what the compiler uses). For example:

package foo;

public class Outer
{
    public static class Nested {}
}

To obtain the Class object for that, you'd need Class.forName("foo.Outer$Nested").

Create an instance of that class with the 'new' keyword in your main activity and then invoke those methods on that object.

BDD bdd = new BDD();
boolean value = bdd.insertarGuia("foo", "bar");

Or make the methods static

Change

public boolean insertarGuia(String g, String d) {

to

public static boolean insertarGuia(String g, String d) {

and in your main method have

boolean value = BDD.insertaGuia("foo", "bar");

It's called polymorphism:
The instance of a class can be treated as instance of that class but also as an instance of every interface the class implements, since it has to implement all the interface's methods. An interface is a contract that says: "The class implementing me offers at least the same operations that I offer."

Every HashMap is a Map, but not every Map is a HashMap.