Common Lisp has some value types, specifically numbers and characters. Any implementation is allowed to copy these objects at any time. For this reason the EQ

Common Lisp has some value types, specifically numbers and characters. Any implementation is allowed to copy these objects at any time. For this reason the EQ function should not be used on numbers or characters, as the results may be unpredictable. The comparison function EQL should be used normally in its place. (Integers and characters also are often represented by "immediate" values that reside inside what would otherwise be a pointer; for these EQL and EQ always do the same thing. But bignums and larger floats allocated on the heap can be different.) It would be interesting to extend Common Lisp to have types that operate similarly. For example, structures that are not compared by object identity but by EQL of their fields. I presume these are the value types being discussed here for Java. One nice thing about value types is they play well with distributed computing. Serialize/deserialize and the values stay the same; no need to have references to objects sitting off in another computer.