Determine the values of $a$ and $b$ such that $y = f \left(x\right)$ will be continuous for all values of $x$.  

$f ( x ) = \left\{ \begin{array} { l l } { 2 x + a \text { for } } & { x \leq - 2 } \\ { x ^ { 2 } - 2 } & { \text { for } - 2 < x \leq 3 } \\ { - x + b } & { \text { for } } { x > 3 } \end{array} \right.$