Room#getArea does work correctly.

float s1[][] = { { 0, 0 }, { 0, 4 }, { 4, 0 }, { 4, 4 } };

This shape has actually an area of 8.

float s1[][] = { { 0, 0 }, { 0, 4 }, { 4, 4 }, { 4, 0 } };

This square shape has an area of 16.