linear algebra - a question how to compute the eigenvalues of a matrix

I have a question:
Suppose I have a $n\times n$ matrix:
$$\begin{bmatrix} 1 & 1 &...& 1 \\ 1 & 1 &...&1 \\ \vdots&\vdots &\ddots & \vdots&\\ 1 & 1 & ...&1 \\ \end{bmatrix}$$
,then is there a easy way to compute the eigenvalues of the matrix?

How can I compute this matrix eigenvalue?