vertical align center text inside div

1display: flex;
2align-items: center

1/*attention, i used this code because i had to center a div with text in another div without text*/
2div{
3  position: relative;
4  top: 25%;
5  bottom: 25%;
6}

1.center {
2  height: 309px;
3  line-height: 309px; /* same as height! */
4}