java.util.Random is a Linear Congruential Generator and Math.random is based on it. That means that both functions produce predictable values.
An attacker could leverage this property against James to eventually "obtain/use" an already "in-use" pseudo-randomly generated number to overwrite things like files, emails, mailboxes, etc. Such scenarios are rather unlikely but still in theory much more feasible than if a true robust and cryptographically strong RNG was used. java.security.SecureRandom has these properties.