InexactVarargsConditional
Conditional expression in varargs call contains array and non-array arguments

Category
Severity
ERROR
Maturity

The problem

When calling a varargs method, you can either pass an explicit array of arguments, or individual arguments:

void f(Object... xs) {
  System.err.println(Arrays.deepToString(xs));
}

Both of the following print [1, 2]:

f(new Object[] {1, 2}) // prints "[1, 2]"
f(1, 2) // prints "[1, 2]"

If the argument to the varargs method is a conditional expression, and either branch is not an array, the result of the expression will be implicitly wrapped in an array.

f(flag ? 1 : 2) // prints [1] or [2]

This means that if one branch is an array and the other branch is not, the array branch will become a multi-dimensional array:

f(flag ? new Object[] {1, 2} : 3); // prints [[1, 2]] or [3]

To avoid the implicit array creation, the other argument can be explicitly wrapped in an array:

f(flag ? new Object[] {1, 2} : new Object[] {3}); // prints [1, 2] or [3]

Or, if the multi-dimensional array was intentional, it can be written explicitly as:

f(flag ? new Object[][] 1 : new Object[] {3}); // prints [[1, 2]] or [3]

Suppression

Suppress false positives by adding an @SuppressWarnings("InexactVarargsConditional") annotation to the enclosing element.