Android™ How to Program, Second Edition

DeckOfCards Method shuffle

Method shuffle (lines 30–46) shuffles the Cards in the deck. The method loops through all 52 Cards. For each Card, a number between 0 and 51 is picked randomly to select another Card, then the current Card and the randomly selected Card are swapped in the array. This exchange is performed by the assignments in lines 42–44. The extra variable temp temporarily stores one of the two Card objects being swapped. The swap cannot be performed with only the two statements

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deck[ first ] = deck[ second ];deck[ second ] = deck[ first ];

If deck[first] is the "Ace" of "Spades" and deck[second] is the "Queen" of "Hearts", after the first assignment, both array elements contain the "Queen" of "Hearts" ...