Can we pass a Single Object as well as as List of Objects in the same Generic PlaceHolders

Question

My question is pretty simple, can we pass a Single Java Object as well as List of Java Object in the same Generic Placeholders in a method.

example: processData(T t)/processData(List<T> t)

is it possible to clubbed this into one method & one generic place holder which can hold both a single Generic object or List of Generic objects in Java

Answer 1

Yes. For example like this:

public class MyWorker<T> {
  public void processData(T t){ }
  public void processData(List<T> t) {}
}

Answer 2

If I understand the question correctly you want a single method that could deal with either a single element or list of certain element type or type-parameter T without overloading.

The closest you can get is to overload and if you want to share the code you could make the single element method delegate into the List method by packing the single element into a singleton list:

class X<T> {
   public void processData(T t) { processData(Collections.singletonList(T)); }
   public void processData(List<T> ts) { ... }; 
} 

However typically you want to customize the code in the single element method to make it run faster in that special case.

If you renounce to List and you are happy to work with arrays instead then you could use a vararg however under the hood you are always passing an array to the method:

class X<T> {
   public void processData(T ... ts) {
       for (T t : ts) { ... };
   } 
} 
...
T x, y, z;
T[] xxx;
...
// the following are all valid calls to processData:
processData(x);
processData(x, y, z);
processData(xxx);