用css给一个元素加边框有哪些方法？

.box{  border: 1px solid #000;}

    .box{      width: 100px;      height: 100px;      background-color: #ccc;      position: relative;    }    .box::after{      position: absolute;      content: '';      top: 0;      left: 0;      bottom: 0;      right: 0;      border: 1px solid #000;    }