How to instantiate generic class and call a method

Question

Right now I have 4 classes which have common method to be called depending on the case as given in below example.

Class1 class1 = new Class1();
Class1 class2 = new Class2();
Class1 class3 = new Class3();
Class1 class4 = new Class4();

MyEnum enum = MyEnum.valueOf(getString()); //getString() will return String "c1" or "c2" or ....

switch(s)
{
case c1 :
class1.add();
break;
case c2 :
class2.add();
break;
case c3 :
class3.add();
break;
case c4 :
class4.add();
break;
}

since there is a possibility of new classes later, I want to make the class initialization and method call generic. Please let me know the best way to achieve it. thanks in advance for suggestions.

Answer 1

I think this is a proper way to do it (without generics):

public interface ICommon {
   public void add();
}

then Class1,Class2,Class3 ,... should implement ICommon interface.

With that I recommend you to create a ClassFactory like this:

public class ClassFactory {

public static ICommon getInstance() {
... //do here whatever it takes to create a concrete instance of ICommon
}

and finally, it would look like this:

ICommon someClass = ClassFactory.getInstance();
someClass.add();

}

EDIT:

Instead of using a switch statement you could add this to your ClassFactory :

public class ClassFactory {

    private static HashMap<String, String> mClassMapping = new HashMap<String, String>();

    public static void registerClass(Class<?> clazz, String tag) {
        String name = clazz.getName();
        mClassMapping.put(tag, name);
    }

    public static ICommon getInstance(String tag) throws ClassNotFoundException, InstantiationException, IllegalAccessException {
        String className = mClassMapping.get(tag);

        if  (null == className) {
            throw new ClassNotFoundException(String.format("There is no class registered for tag: %s", tag));
        }

        Class<?> aClass = Class.forName(className);

        return (ICommon)aClass.newInstance();
    }
}

Finally you could do this: At some starting point register your classes:

ClassFactory.registerClass(Class1.class, "c1");
ClassFactory.registerClass(Class2.class, "c2");
...

Then get an instance like this:

String tag = ...//get tag associated to the class somehow; 

ICommon classInstance = ClassFactory.getInstance(tag);   //i.e tag == "c1"
classInstance.add();

Answer 2

@user1849139

1) public interface genaricInterface{ public void commonMethod(); }

2)implement above interface to your class and override the method

3)public Class class1 implements genaricInterface{ public void commonMethod(){ //write your logic here for class1 } }

4)Like above class you can implement to n-number of classes in java after that

5)create instance like genaricInterface gi = new class1();

6)call method gi.commonMethod();