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.