Java中以对象为参数的泛型方法

Question

There are two classes A and B which have similar methods. How to write a generic method that takes either one of the class object as argument and will be able to call the methods of that class.

Edit : I do not have control over class A, B. I get them only as arguments. So i cannot modify add them.

public class methods {

    public static void main(String[] args) {
        new methods().getName(new B());
        new methods().getName(new A());
    }

    private <T> void getName(T obj){
        // obj.getName()
    }
}

class A {

    String name = "ClassA";

    public void getName(){
        System.out.println(name);
    }

}

class B {

    String name = "ClassB";

    public void getName(){
        System.out.println(name);
    }

}

Answer 1

If the two classes do not implement a common interface, you could use reflection, but this is not type safe (you won't get any compilation errors if A or B no longer support getName() and reflection is much slower than calling a method directly.

You could also implement two adapters that share an interface and use those (with generics):

interface Wrapper {
    String getName();
}

class WrapperA implements Wrapper {
    final private A a;
    public WrapperA(A wrapped) {
        this.a = wrapped;
    }
    @Override public String getName() {
        return a.getName();
    }
}

Answer 2

Below solution uses instanceof operator in the generic method to reach your output.

   public static void main(String[] args){
        new methods().getName(new B());
        new methods().getName(new A());
    }

    private <T> void getName(T obj) {
        if(obj instanceof B){
            ((B) obj).getName();
        }
        else{
            ((A) obj).getName();
        }
    }