How many stereoisomers does this molecule have?

Key Idea : (i) Number of optical isomers $=2^n$ where, $n=$ number of dissimilar asymmetric carbon atoms. (ii) Number of geometrical isomers $=2^{\hbar}$ where, $n=$ number of double bond only when the two ends of the chain are different
Here, number of optical isomers $=2^1=2$ Number of geometrical isomers $=2^1=2$ Hence, number of stereoisomers $=2+2=4$