This document contains code for 20 programs written in Java and the Android Studio environment. The programs calculate areas, perimeters, volumes, and unit conversions for geometric shapes and measurements. Each program contains code to retrieve input values from edit text fields, perform calculations, and display output in text views. The programs cover calculations and conversions for squares, triangles, rectangles, pentagons, octagons, cubes, cylinders, cones, as well as conversions between feet/yards, centimeters/inches, kilometers/meters, minutes/seconds, hours/seconds, meters/centimeters, and seconds/minutes.