Unlocking Bootloader Simplest Method

 1. You Have to First Instal Flashtool from Here

 

 2. Then you have to instal specific driver of your devices ,Mine is Xperia U

 

3. After instaling Driver ,Start flashtool.Where you seen "BLU" in dark colour.

 

4.Now connect your phone in Flasmode(Volume Up+Power key).It show green indication at           bottom of the transparent bar.

 

5.Click on BLU 

 

That's It now your phone is bootloder unlocked