For instance, in Go everything is passed by value. If you want to pass a reference, you must pass a reference type (like a pointer). This means that you can pass around structs without having to put them on the heap. In JVM-land, nearly everything is passed by reference, and the data must go on the heap.
Relatedly, in Go if you allocate an array of n values of type T, the size of that array in memory is n * sizeof(T), and the items are laid out sequentially in memory. There are no other bookkeeping data structures and no indirection.
Here's a story about one project's struggle with data structures and Java: http://marc.info/?l=git&m=124111702609723
Relevant quote:
JGit struggles with not having an efficient way to represent a SHA-1.
C can just say "unsigned char[20]" and have it inline into the
container's memory allocation. A byte[20] in Java will cost an
*additional* 16 bytes of memory, and be slower to access because
the bytes themselves are in a different area of memory from the
container object. We try to work around it by converting from a
byte[20] to 5 ints, but that costs us machine instructions.
In Go, you would just write [20]byte. If you wanted a struct with a field of [20]byte you can do so, and all it costs is the 20 bytes.