提取通用 class 的字段

Question

I have multiple classes which all have one common field. I'm writing a method which deals with extracting this common field. For example:

class A{
    ..
    String blah;
    ..
}

class B{
    ..
    String blah;
    ..
}

So instead of writing multiple methods for each class type, can this be achieved using a method that accepts a generic class? What I want is to have a method of type:

void func(List <T> data){
    for(T t:data){
        print t.blah()
    }
}

I know the above code is incorrect but how do we get the similar functionality?

Answer 1

First, create an interface that holds any common method signatures.

interface Blah {
    String getBlah();
}

Then, make your existing classes A and B implement that interface. (Use @Override to ensure that you're properly overriding the method.)

Finally, in func , take a list of objects that implement that interface.

void func(List<? extends Blah> data) {
    for (Blah t : data) {
        System.out.println(t.getBlah());
    }
}