How can I write a method that will accept any array of any type (including primitives) as a parameter?
For instance, I would like both of the following calls to work:
int[] intArray = {1, 2, 3};
String[] strArray = {"1", "2"};
hasSize(intArray, 3);
hasSize(strArray, 2);
The closest I've gotten so far is:
public static <T> boolean hasSize(T[] array, int expectedSize)
{
return (array.length == expectedSize);
}
...but this doesn't work for primitives.
A primitive array and an object array don't share are base class except Object.
So the only possibility would be to accept an object and inside the method check if it is an array
public static <T> boolean hasSize(Object x, int expectedSize)
{
return (x != null) && x.getClass().isArray() ?
java.lang.reflect.Array.getLength(x) == expectedSize :
false;
}
Of course this also accepts non-arrays, probably not the solution you want.
For this reason the JDK mostly provides identical methods for object arrays and primitive arrays.
If I recall correctly, you can't create a generic array that you expect to have take primitives, as the primitives themselves are not classes and not available to the Java generics system.
Rather, your incoming array would have to be an Integer[], Double[], etc.
You can do something like this
public class A {
public static void main (String[] args) {
int[] intArray = {1, 2, 3};
String[] strArray = {"1", "2"};
hasSize(Arrays.asList(intArray), 3);
hasSize(Arrays.asList(strArray), 2);
}
public static <T> boolean hasSize(List<T> array, int expectedSize)
{
return (array.size() == expectedSize);
}
}
This is not exactly what you want. But you can take advantage of generic mechanism by passing the array to list, and the autoboxing do the work for you.
If this approach is good for you then ok, but if is not a good approach unfortunately the generic mechanism does not support primitive types, so you have to override the method for each array type.
As mention above you can't mix primitive array and Object array, you have to use wrapper class . If function is going to except variable arguments then one the way to write that is using vargs notion
public static <T> void process(T...args) {
System.out.println(Arrays.toString(args));
}
this notion is used in java internal API
