Here's Java getting compiled to actual x86-64 code (mov $0x2a,%edx; add %edx,%eax).

  $ cat FortyTwo.java 
  public class FortyTwo
  {
          public static int fortytwo(int x) {
          	return x + 42;
          }
  }
  
  $ gcj-4.9 -c FortyTwo.java 

$ objdump -S FortyTwo.o

  FortyTwo.o:     file format elf64-x86-64
   
   
  Disassembly of section .text:

  <snip>
    
  0000000000000022 <_ZN8FortyTwo8fortytwoEJii>:
  {
          public static int fortytwo(int x) {
          	return x + 42;
    22:	55                   	push   %rbp
    23:	48 89 e5             	mov    %rsp,%rbp
    26:	48 83 ec 20          	sub    $0x20,%rsp
    2a:	89 7d ec             	mov    %edi,-0x14(%rbp)
    2d:	b8 00 00 00 00       	mov    $0x0,%eax
    32:	48 89 c7             	mov    %rax,%rdi
    35:	b8 00 00 00 00       	mov    $0x0,%eax
    3a:	e8 00 00 00 00       	callq  3f <_ZN8FortyTwo8fortytwoEJii+0x1d>
    3f:	8b 45 ec             	mov    -0x14(%rbp),%eax
    42:	89 45 fc             	mov    %eax,-0x4(%rbp)
    45:	8b 45 fc             	mov    -0x4(%rbp),%eax
    48:	ba 2a 00 00 00       	mov    $0x2a,%edx
    4d:	01 d0                	add    %edx,%eax
    4f:	c9                   	leaveq 
    50:	c3                   	retq