从类中扩展的泛型究竟是什么意思？

public class MyClass<T> {
    private T data;

    public void setData(T data) {
        this.data = data;
    }

    public T getData() {
        return data;
    }
}

public interface MyInterface<T> {
    void doSomething(T data);
}

public class MySubClass extends MyClass<String> {
    // ...
}

public class MySubClass2 implements MyInterface<Integer> {
    @Override
    public void doSomething(Integer data) {
        // ...
    }
}