4. In the Cartesian coordinate plane, the curve
$$
|x-1|+|x+1|+|y|=3
$$

encloses a figure with an area of $\qquad$
4.5.

When $y \geqslant 0$,
$$
\begin{aligned}
y & =3-|x-1|-|x+1| \\
& =\left\{\begin{array}{ll}
3+2 x, & x \leqslant-1 ; \\
1, & -11 .
\end{array}\right.
\end{aligned}
$$

Its graph is the broken line $A B C D$ in Figure 1.
When $y \leqslant 0$, it is only necessary to flip the above broken line along the $x$-axis.
Therefore, the curve $|x-1|+|x+1|+|y|=3$ encloses