How to create instance of subclass with constructor from super class

Question

I\'d like to create a registry for classes which are subclasses of a super class. The classes are stored in a map which acts as registry. A class is picked from the registry dep

Answer 1

You are using this line to get the constructor

clazz.getDeclaredConstructor( Object.class);

But your Subclass2 does not have a single argument constructor hence the exception is thrown.

Use clazz.getDeclaredConstructors() method instead and invoke constructor based on parameters count.

            BaseClass instance;
            // get constructor with parameter
            Constructor constructor = clazz.getDeclaredConstructors()[0];
            if (constructor.getParameterCount() == 1) {
                instance = (BaseClass) constructor.newInstance(key);
            } else {
                instance = (BaseClass) constructor.newInstance();
            }