This UDF is used to check whether the String input is an Integer.
Note this function checks for Integer range -2,147,483,648 to 2,147,483,647.
If range is not important, use IsNumeric instead if you would like to check if a String is numeric.
Also IsNumeric performs slightly better compared to this function.
Nested Class Summary
Nested classes/interfaces inherited from class org.apache.pig.EvalFunc
This callback method must be implemented by all subclasses. This
is the method that will be invoked on every Tuple of a given dataset.
Since the dataset may be divided up in a variety of ways the programmer
should not make assumptions about state that is maintained between
invocations of this method.