The program iterates over the 'furnitures' array and appends specific characters based on their indices. It starts by initializing 'index' as 'i + 1', then appends this index, a period, a parenthesis, and the character at the 'i'th position of each 'furniture' string followed by a comma. If the 'index' is less than 'furnitures.length', it appends '|', otherwise, it appends only the character and the comma. The StringBuilder is then modified by deleting the last comma and space, and adding brackets at the beginning and end. For the provided 'furnitures' array: {'Door', 'Window', 'Chair'}, the resulting string after processing will be '[0). o, | 1). i, | 2). r]'.