How to shuffle the elements in an ArrayList?

Question

Hi, everyone
I write the following method to shuffle the elements of an ArrayList of Question type, and then Print the questions out
public void shuffle()
        System.out.println ("This is a test created randomly");
        Random generator = new Random ();
        for (int i = 0; i < questions.size(); i++)
            int randomQuestion = generator.nextInt(questions.size());
            Question temp1 = questions.get(i);
            Question temp2 = questions.get(randomQuestion);
            Question temp3 = temp1;
            temp1 = temp2;
            temp2 = temp3;
            System.out.println ("" + (i+1) + ". " + questions.get(randomQuestion).getQuestion()+"\n");  
    }      But I find that the elements of the ArrayList have not been swapped, why?
Thank you.

Answer 1

temp1, temp2 and temp3 are all local variables. They're put on the stack at the beginning of the function and popped off at the end. You are never modifying the collection.