A continuous function $f ( x )$ satisfies
$$f ( x ) = e ^ { x ^ { 2 } } + \int _ { 0 } ^ { 1 } t f ( t ) d t$$
What is the value of $\int _ { 0 } ^ { 1 } x f ( x ) d x$? [3 points]\\
(1) $e - 2$\\
(2) $\frac { e - 1 } { 2 }$\\
(3) $\frac { e } { 2 }$\\
(4) $e - 1$\\
(5) $\frac { e + 1 } { 2 }$