 <p>Java 7 supports the feature of having underscores in the numeric literals to improve the readability of the values being assigned.</p> <p>but the underscore usage is restricted to be in between two numeric digits, i.e not at the beginning or ending of the numeric values but should be confined between two digits, should not be as a prefix to l,f used to represent long and float values and not in between radix prefixes also.</p>