what happen IF condition is executing and interrupt is came?
Although you're describing C/Java/some-HLL, your CPU is executing machine code instructions. (HLL is High-Level Language.)

When the CPU services the interrupt, it will complete the instruction it is executing, save some of the program state and subroutine-call an Interrupt Service Routine (ISR). The ISR must complete its task and return from the interrupt. The CPU will restore the program state and should carry on executing the main program as if nothing had happened.

The lines of your program are made up of one or more CPU instructions. You can see this by looking into the debugger or output files from your compiler and seeing the lines of assembly language generated for each program line. (1 assembly language line is 1 CPU instruction.)

The various parts of an if-then-else-end clause (or equivalent for your HLL) are all carried out by these CPU instructions. There is nothing more special about getting an interrupt anywhere during there - the interrupt can occur anywhere.