Just like its name, FJ has only 2 valid symbols: f and j, it is case sensitive.
When typing a program in you computer, you just have to directly tap on the keys under your index finger, so it is easy to type.
Here is the brainfuck to FJ conversion table.
|+||fff||Increment the memory cell under the pointer|
|-||ffj||Decrement the memory cell under the pointer|
|,||fjf||Input a character and store it in the cell at the pointer|
|.||fjj||Output the character signified by the cell at the pointer|
|<||jff||Move the pointer to the left|
|>||jfj||Move the pointer to the right|
|[||jjf||Jump past the matching |
|]||jjj||Jump back to the matching |
Since brainfuck is Turing complete, FJ is.