Problem - Shuffle an Array

You need to shuffle an array so that every permutation is equally likely. This is harder than it sounds.

Given an array of integers, implement a class that can reset the array to its original state and shuffle it randomly. Each permutation must have equal probability of $\frac{1}{n!}$ where $n$ is the array length.

Before reading on, think about this: if you pick random swaps without a plan, will every permutation have equal chance?