DateFormat does not mention IllegalArgumentException for invalid style args

Summary

Make IllegalArgumentException apparent for the DateFormat factory methods in the specification.

Problem

The DateFormat static factory methods throw an IllegalArgumentException if the style parameter is less than 0 (FULL) or greater than 3 (SHORT). This is not specified in the class description or method descriptions.

Solution

There are a number of static factory methods that take the style parameter. To avoid redundancy, introduce a sentence in the class description to make this behavior apparent (as opposed to each method).

Specification

In the class description,

- * <p>{@code DateFormat} provides many class methods for obtaining default date/time
+ * <p>{@code DateFormat} provides static factory methods for obtaining default date/time
  * formatters based on the default or a given locale and a number of formatting
- * styles. The formatting styles include {@link #FULL}, {@link #LONG}, {@link #MEDIUM}, and {@link #SHORT}. More
- * detail and examples of using these styles are provided in the method
+ * styles. The formatting styles include {@link #FULL}, {@link #LONG}, {@link #MEDIUM}, and {@link #SHORT}.
+ * For any of the factory methods with the parameter <i>style</i>, an {@code
+ * IllegalArgumentException} will be thrown if <i>style</i> is not equal to any
+ * of the defined formatting styles. More detail and examples of using these styles are provided in the method
  * descriptions.
  *