> This wastage does happens only in reference types? Tomorrow say if value types are been created, then these sort of issue will get resolved?

That would solve most of the issue, yes.

> Why of constant zeros? And in the line your saying "-- 1TB is 2^40", your referring 1TB of cache line?

He was not referring to cache line or anything like that. He was referring to the fact if you can address just 40 bits, upper 24 bits in a 64-bit pointer are wasted in a pointer. I think on x86 real virtual address size is currently 48 bits, so upper 16 bits are "wasted". This wastage will occur with heaps larger than 32 GB when using compressed pointers JVM option. And of course 4 GB (or 2 GB?) with that JVM option disabled.

Similarly, if you use "bool" type, it still takes a byte in current JVM implementations. So you could say 7 bits are wasted there.