如何最有效地选择3个随机问题并以随机顺序对其进行排序？

Question

I am working on a project for school, and was asked to create a "store" that sells silly items. After the user adds the appropriate number of items to his/her cart, they select the option to checkout. After doing so, the user is prompted with a trivia question, based on Star Wars knowledge.

For bonus points in the class, I need to create a file that stores several questions and answers, and then check if they are correct.

I currently have 2 files, a trivaQ.txt and a triviaA.txt. They both hold "Question1"-"Question10" and "Answer1"-"Answer10". Question1's answer is Answer1, and Question2's answer is Answer2, and so on.

I wrote a simple ReadFile class that can access the file, and I am trying to build a method that will select the correct answer (the same as the question index) and then 2 other random ones.

Here is the current code:

        public int askA(){

    int cAnswer = Question;
    int answer1= (int)(Math.random() *10);
    int answer2= (int)(Math.random() *10);



    while(answer1 == cAnswer || answer1 == answer2){
        answer1 = (int)(Math.random() *10);
    }
    while(answer2 == cAnswer || answer2 == answer1){
        answer2 = (int)(Math.random() *10);

    }


    int x = random.nextInt(3)+1;
    int y = random.nextInt(3)+1;
    int z = random.nextInt(3)+1;


    while( x == y || x == z){
        x = random.nextInt(3)+1;
    }

    while( y == x || y == z){
        y = random.nextInt(3)+1;
    }

    while( z == x || z == y){
        z = random.nextInt(3)+1;
    }


    if(x > y && x > z){
        //x is first
        if(y > z){
            //y is second
            //z is third
            System.out.println("[1.] " + itemData.get(cAnswer));
            System.out.println("[2.] " + itemData.get(answer1));
            System.out.println("[3.] " + itemData.get(answer2));
            System.out.println("Answer is 1");

        }else{
            //z is second
            //y is third
            System.out.println("[1.] " + itemData.get(cAnswer));
            System.out.println("[2.] " + itemData.get(answer2));
            System.out.println("[3.] " + itemData.get(answer1));
            System.out.println("Answer is 1");
        }


    }else if(y > x && y > z){
        //y is first
        if(x > z){
            //x is second
            //z is third
            System.out.println("[1.] " + itemData.get(answer1));
            System.out.println("[2.] " + itemData.get(cAnswer));
            System.out.println("[3.] " + itemData.get(answer2));
            System.out.println("Answer is 2");
        }else{
            //z is second
            //x is third
            System.out.println("[1.] " + itemData.get(answer1));
            System.out.println("[2.] " + itemData.get(answer2));
            System.out.println("[3.] " + itemData.get(cAnswer));
            System.out.println("Answer is 2");
        }


    }else if(z > y && z > x){
        //z is first
        if(y > x){
            //y is second
            //x is third
            System.out.println("[1.] " + itemData.get(answer2));
            System.out.println("[2.] " + itemData.get(answer1));
            System.out.println("[3.] " + itemData.get(cAnswer));
            System.out.println("Answer is 3");
        }else{
            //x is second
            //y is third
            System.out.println("[1.] " + itemData.get(answer2));
            System.out.println("[2.] " + itemData.get(cAnswer));
            System.out.println("[3.] " + itemData.get(answer1));
            System.out.println("Answer is 3");
            }
        }
    System.out.println("X is - " + x);
    System.out.println("CorrectAnswer --- " + cAnswer);


    return x;

}

This method currently doesn't work as I want it to. It selects a question and it selects the correct answer and 2 random answers, however; it does not sort them in the proper order.

I check if the returned value x is equivalent to the user input, and while it works probably 6/10 times, it fails 4/10 times.

Is there a more efficient way to do this? What is going wrong with my code?

Answer 1

Easy as :

java.util.Collections.shuffle(itemData);
result = FluentIterable.from(itemData).limit(3).toList(); //(using Google Guava)
result = itemData.stream().limit(3).collect(Collectors.toList());//(using java 8):

• ref : http://docs.oracle.com/javase/7/docs/api/java/util/Collections.html
• ref : https://code.google.com/p/guava-libraries/

After you call shuffle you can alternatively read values from

itemData.get(0)
itemData.get(1)
itemData.get(2) 

Answer 2

The easiest way for me to get it to work without having to use Google guava etc., was by creating another integer reAnswer.

        int reAnswer = 0;

After every:

        //z is second
        //y is third
        System.out.println("[1.] " + itemData.get(cAnswer));
        System.out.println("[2.] " + itemData.get(answer2));
        System.out.println("[3.] " + itemData.get(answer1));
        System.out.println("Answer is 1");

I would add:

        reAnswer = 1;

Or whatever the correct answer corresponded with. I then returned the value reAnswer from the method and checked it in the main file. It was a simple work around. Thank you for the help everyone, I just didn't think about doing it this way until now.

• Connor