是否可以将对象类型信息传递给泛型方法

Question

Im kinda new to the concept of generic types etc. But the question is very simple, i want to write a method that takes two arrays of the same type as parameters and returns one single array of the same type. However, the type can be any class defined by me.

I have tried using the generic java Object class, but then I cant cast it back to my type. Isn't there a way to pass the type information to the function so that it knows what kind of type it has to return?

String[] a = {"sfsdf", "dwedwe"};
String[] b = {"anda", "vuela"};

String[] result = (String[]) addArrays(a, b); >> error type mismatch

Object[] addArrays(Object[] o1, Object[] o2){
    Object[] result = new Object[o1.length + o2.length];

    for(int i=0;i<o1.length;i++){
      result[i] = o1[i];
    }

    for(int i=o1.length;i<result.length;i++){
      result[i] = o2[i-o1.length];
    }

  return result;   
}

Answer 1

Better to avoid mixing arrays and generics. If you must use arrays, this should work:

<T> T[] addArrays(T[] o1, T[] o2) {
    T[] result = Arrays.copyOf(o1, o1.length + o2.length);
    System.arraycopy(o2, 0, result, o1.length, o2.length);
    return result;
}

Note that the array type returned will be the same as o1 .

Answer 2

Here you can find some quick example of implementation:

public <T> List<T> doList(T param1, T param2) {
    List<T> result = new ArrayList<>();
    result.add(param1);
    result.add(param2);

    return result;
}

And here is a usage

List<Cat> myCatList = doList(new Cat(), new Cat());
List<Dog> dogList = doList(new Dog(), new Dog());

You can read more about generics here