First make a xml file with contents shown below and name it border.xml and place it inside the layout folder inside the res directory
<?xml version="1.0" encoding="UTF-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">
<stroke android:width="1dp" android:color="#0000" />
<padding android:left="0dp" android:top="1dp" android:right="0dp"
android:bottom="1dp" />
</shape>
After that inside the code use
TextView tv = (TextView)findElementById(R.id.yourTextView);
tv.setBackgroundResource(R.layout.border);
This will make a black line on top and bottom of the TextView.