Printing random string from ArrayList class into JLabel text

Question

I am creating a quiz

I have a class which contains the GUI and code for a location to place questions that will be asked in my application. The class below will be used to hold a JLabel component (Among other UI elements), and should display a random question from a list of questions given to it. I have saved each of these 'question lists'as an ArrayList in another class.

I am aware you would have to use a random number generator to pick a line from the list of questions, by generating an index number, then using this to retrieve a line from the array to use as the text to display in the JLabel

I am unsure however how to do this when it comes to the actual code, please could anybody help.

My code is as follows:

package ZillionaireGUI;

import java.awt.Frame;

import javax.swing.ButtonGroup;
import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JRadioButton;
import javax.swing.SwingUtilities;


public class questionDialog extends JDialog {
private JLabel Question;
private JRadioButton answerThree;
private JRadioButton answerFour;
private JRadioButton answerTwo;
private JRadioButton answerOne;
public questionDialog(Frame parent) {
    super(parent);
}


public questionDialog(JFrame frame) {
    super(frame);
    initGUI();
}

private void initGUI() {
    try {

        getContentPane().setLayout(null);

        Question = new JLabel();
        getContentPane().add(Question);
        Question.setText("jLabel1");
        Question.setBounds(39, 127, 383, 29);

        answerOne = new JRadioButton();
        getContentPane().add(answerOne);
        answerOne.setText("jRadioButton1");
        answerOne.setBounds(26, 183, 93, 20);

        answerTwo = new JRadioButton();
        getContentPane().add(answerTwo);
        answerTwo.setText("jRadioButton1");
        answerTwo.setBounds(130, 183, 93, 20);

        answerThree = new JRadioButton();
        getContentPane().add(answerThree);
        answerThree.setText("jRadioButton1");
        answerThree.setBounds(247, 183, 93, 20);

        answerFour = new JRadioButton();
        getContentPane().add(answerFour);
        answerFour.setText("jRadioButton1");
        answerFour.setBounds(360, 183, 93, 20);

        ButtonGroup group = new ButtonGroup();
        group.add(answerOne);
        group.add(answerTwo);
        group.add(answerThree);
        group.add(answerFour);


        this.setSize(490, 393);
    } catch (Exception e) {
        e.printStackTrace();
    }
}

}

import java.util.*;
public class Questions {
public static void main(String[] args) {
    ArrayList<String> SPOquestions = new ArrayList<String>(); // adding the sports questions for the quiz

    SPOquestions.add("Who won the 2005 Formula One World Championship?");
    SPOquestions.add("Which team has the most Formula One Constructors titles?");
    SPOquestions.add("In what year did Roger Federer win his first 'Grand Slam'?");
    SPOquestions.add("How many 'Grand Slams' has Rafael Nadal won?");
    SPOquestions.add("Who has scored the most amount of goals in the Premier League?");
    SPOquestions.add("Who has won the most World Cups in football?");
    SPOquestions.add("How many MotoGP titles does Valentino Rossi hold?");
    SPOquestions.add("Who was the 2013 MotoGP champion?");
    SPOquestions.add("Who won the 2003 Rugby World Cup?");
    SPOquestions.add("In rugby league, how many points are awarded for a try?");
    SPOquestions.add("Who is the youngest ever snooker World Champion?");
    SPOquestions.add("In snooker, what is the highest maximum possible break?");
    SPOquestions.add("How many majors has Tiger Woods won?");
    SPOquestions.add("In golf, what is the tournament between the USA and Europe called?");
    SPOquestions.add("How many World Championships has darts player Phil Taylor won?");
    SPOquestions.add("What is the maximum possible amount of points a player can earn from throwing three darts?");
    SPOquestions.add("How many gold medals did Michael Phelps win at the 2008 Beijing Olympics?");
    SPOquestions.add("Who won the 2012 Olympic 100 metres mens race?");
    SPOquestions.add("Which of these events are not a part of the heptathlon?");
    SPOquestions.add("When was the first modern Olympics held?");

    ArrayList<String> MUSquestions = new ArrayList<String>(); // adding the music questions

    MUSquestions.add("'Slash' was a member of which US rock band?");
    MUSquestions.add("Brian May was a member of which English rock band?");
    MUSquestions.add("What is the name of the music festival held annually in the town of Boom, Belgium?");
    MUSquestions.add("The rapper Tupac Shakuer '2Pac' died in which year?");
    MUSquestions.add("Which of these bands headlined the 2013 Glastonbury music festival?");
    MUSquestions.add("Which of these people designed the 'Les Paul' series of guitars?");
    MUSquestions.add("Keith Moon was a drummer for which English rock band?");
    MUSquestions.add("Kanye West has a total of how many Grammy awards?");
    MUSquestions.add("Beyonce Knowles was formally a member of which US group?");
    MUSquestions.add("In which US city was rapper 'Biggie Smalls' born?");
    MUSquestions.add("Michael Jackson's first number one single in the UK as a solo artist was what?");
    MUSquestions.add("The best selling album of all time in the UK is what?");
    MUSquestions.add("The best selling album of all time in the US is what?");
    MUSquestions.add("What is the artist known as 'Tiesto's real name?");
    MUSquestions.add("Which of these was not a member of The Beatles?");

    ArrayList<String> GENquestions = new ArrayList<String>(); // adding general knowledge questions

    GENquestions.add("Who was the second President of the United States?");
    GENquestions.add("The youngest son of Bob Marley was who?");
    GENquestions.add("In the film '8 Mile', the character portrayed by Eminem is known as what?");
    GENquestions.add("What is the capital city of New Zealand?");
    GENquestions.add("What is the capital city of Australia?");
    GENquestions.add("How many millilitres are there in an English pint?");
    GENquestions.add("What was the biggest selling game for the PS2 worldwide?");
    GENquestions.add("What is the last letter of the Greek alphabet?");
    GENquestions.add("Who created the television series Futurama?");
    GENquestions.add("A word which reads the same backwards as it does forwards is known as a what?");
    GENquestions.add("A 'baker's dozen' consists of how many items?");
    GENquestions.add("World War 1 officially occured on which date?");
    GENquestions.add("'Trouble and strife' is cockney rhyming slang for what?");
    GENquestions.add("Who was the last Prime Minister to hail from the labour party in the UK?");
    GENquestions.add("WalMart is the parent company of which UK based supermarket chain?");




}

}

Answer 1

First, you need to generate a random number based on the size of your array. Get a random value in the range of 0.0 - 1.0 from Math.random() and multiply it by the size of your questions array (for example, MUSquestions.size()) - that will give you your random index into the array.

Then. use the ArrayList get method, passing in the index, to get the string you want.

Answer 2

I would definitely use the collections.shuffle this way : List arrlist = new ArrayList();

  // populate the list
  arrlist.add("A");
  arrlist.add("B");
  arrlist.add("C");  

  System.out.println("Initial collection: "+arrlist);

  // shuffle the list
  Collections.shuffle(arrlist);

  System.out.println("Final collection after shuffle: "+arrlist);

Answer 3

To get a random number:

Random rand = new Random();

// nextInt is normally exclusive of the top value,
// so add 1 to make it inclusive
int randomNum = rand.nextInt((max - min) + 1) + min;

Read more here : How do I generate random integers within a specific range in Java?

To use it to access a random question

String randomQuestion=SPOquestions.get(randomNum);

And to show it in the label

Question.setText(randomQuestion);