Default Need help on unlocking bootloader

Okay so yesterday after a fee hours of struggle I finallymanaged to root my xperia J but after *#*#7373823#*#*# it said my bootloader can not be unlocked and this is a massive problem for me because the only reason I rooted was for Custom Roms so can anybody tell me whether or not its still possible to unlock the bootloader and if so how?

Thanks in advance

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Device: Galaxy S3 (i9300)
ROM: Stock (4.3)
Kernel: Boeffla Kernel
Root Access: Yes

Device: Xperia J
ROM: Stock
Kernel: Stock
Root Access: No