How to pull random rows from a database but ensure every row is selected before any are repeated?

Question

I am doing a project on the blackberry. There are two XML databases, Full & Lite. In total there are 350 questions in Full and 20 questions in Lite. When a user takes the Full test, 50 questions are randomly asked from the full set of 350, chosen at random (for Lite it's 10 questions). As the user retakes the test, I want to ensure every question has been asked before questions are repeated, so the user could take the Full test 7 times without seeing a duplicated question (50 questions per try times 7 tries is all 350 questions). I want the question to be generated randomly as well as being unique, and I want to store it in memory so the person leaves after one test and returns later they still won't see duplicates

AppMain Page

//#preprocess
package com.firstBooks.series7;

import net.rim.device.api.ui.UiApplication;

import com.firstBooks.series7.ui.screens.HomeScreen;


public class AppMain extends UiApplication implements AppConfig{

    public static String _xmlFileName;  
    public static boolean _Lite;    
    public static int _totalNumofQuestions;

    public static void initialize(){
         //#ifndef FULL  
           /* 
           //#endif 
              _xmlFileName = "/res/Series7_FULL.xml";
              _totalNumofQuestions = 50;
              _Lite = false;
           //#ifndef FULL 
           */  
        //#endif 

        //#ifndef LITE  
           /* 
           //#endif 
             _xmlFileName = "/res/Series7_LITE.xml";
             _totalNumofQuestions = 10;
             _Lite = true;
           //#ifndef LITE 
           */  
         //#endif 
    }

    private AppMain() {
        initialize();
        pushScreen(new HomeScreen());
    }

    public static void main(String args[]) {
        new AppMain().enterEventDispatcher();
    }
}

XMLParser page

package com.firstBooks.series7.db.parser;

import java.io.IOException;
import java.io.InputStream;
import java.util.Vector;

import net.rim.device.api.xml.parsers.DocumentBuilder;
import net.rim.device.api.xml.parsers.DocumentBuilderFactory;
import net.rim.device.api.xml.parsers.ParserConfigurationException;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;

import com.firstBooks.series7.AppMain;
import com.firstBooks.series7.db.Question;

public class XMLParser {

    private Document document;
    public static Vector questionList;

    public XMLParser() {                 
        questionList = new Vector();
    }

    public void parseXMl() throws SAXException, IOException,
            ParserConfigurationException {

        // Build a document based on the XML file.
        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
        DocumentBuilder builder = factory.newDocumentBuilder();
        InputStream inputStream = getClass().getResourceAsStream(AppMain._xmlFileName);

        document = builder.parse(inputStream);
    }

    public void parseDocument() {
        Element element = document.getDocumentElement();

        NodeList nl = element.getElementsByTagName("question");

        if (nl != null && nl.getLength() > 0) {
            for (int i = 0; i < nl.getLength(); i++) {
                Element ele = (Element) nl.item(i);
                Question question = getQuestions(ele);
                questionList.addElement(question);
            }
        }
    }

    private Question getQuestions(Element element) {

        String title = getTextValue(element, "title");
        String choice1 = getTextValue(element, "choice1");
        String choice2 = getTextValue(element, "choice2");
        String choice3 = getTextValue(element, "choice3");
        String choice4 = getTextValue(element, "choice4");
        String answer = getTextValue(element, "answer");
        String rationale = getTextValue(element, "rationale");

        Question Questions = new Question(title, choice1,
                choice2, choice3, choice4, answer, rationale);

        return Questions;
    }

    private String getTextValue(Element ele, String tagName) {
        String textVal = null;
        NodeList nl = ele.getElementsByTagName(tagName);
        if (nl != null && nl.getLength() > 0) {
            Element el = (Element) nl.item(0);
            textVal = el.getFirstChild().getNodeValue();
        }

        return textVal;
    }
}

DBMain Page

package com.firstBooks.series7.db;

import java.util.Random;



import com.firstBooks.series7.AppMain;
import com.firstBooks.series7.db.parser.XMLParser;

public class DBMain {

    public static String answer = "";
    public static String selectedAnswer = "";
    public static Question curQuestion;
    public static int currQuesNumber = 1;
    public static int correctAnswerCount = 0;
    public static int totalNumofQuestions = AppMain._totalNumofQuestions ;

    static int quesNum[] = new int[XMLParser.questionList.size()];
    static int quesCount = -1;

    static{ 
        initialize();   
    }

    private static void initialize(){

        Random rgen = new Random();  // Random number generator

        //--- Initialize the array 
        for (int i=0; i<quesNum.length; i++) {
            quesNum[i] = i;
        }



        //--- Shuffle by exchanging each element randomly
        for (int i=0; i< quesNum.length; i++) {
            int randomPosition = rgen.nextInt(quesNum.length);
            //System.out.println("The value of RANDOMPOSITION is:"+randomPosition);
            int temp = quesNum[i];
            //System.out.println("The value of TEMP is:"+temp);
            quesNum[i] = quesNum[randomPosition];
            System.out.println("The value of QUESNUM is:"+quesNum[i]);
            quesNum[randomPosition] = temp;
            System.out.println("The value of NEWQUESNUM is:"+quesNum[randomPosition]);
        }
    }

    /*Changed the code to get a unique random number
     * @author: Venu     
    */
    public static int getQuestionNumber() {
        quesCount++;

        if(quesCount < quesNum.length){

            return quesNum[quesCount];

         }
        else{ 
           initialize();
           quesCount = -1;
           return getQuestionNumber();
        }
    }
}

Question Page

package com.firstBooks.series7.db;

public class Question {

    String title;
    String choice1;
    String choice2;
    String choice3;
    String choice4;
    String answer;
    String rationale;

    public Question(String title, String choice1, String choice2,
            String choice3, String choice4, String answer, String rationale) {

        this.title = title;
        this.choice1 = choice1;
        this.choice2 = choice2;
        this.choice3 = choice3;
        this.choice4 = choice4;
        this.answer = answer;
        this.rationale = rationale;
    }

    public String getTitle() {
        return title;
    }

    public String getChoice1() {
        return choice1;
    }

    public String getChoice2() {
        return choice2;
    }

    public String getChoice3() {
        return choice3;
    }

    public String getChoice4() {
        return choice4;
    }

    public String getAnswer() {
        return answer;
    }

    public String getRationale() {
        return rationale;
    }
}

TestScreen Page

package com.firstBooks.series7.ui.screens;

import net.rim.device.api.ui.Field;
import net.rim.device.api.ui.FieldChangeListener;
import net.rim.device.api.ui.Graphics;
import net.rim.device.api.ui.Manager;
import net.rim.device.api.ui.MenuItem;
import net.rim.device.api.ui.UiApplication;
import net.rim.device.api.ui.component.LabelField;
import net.rim.device.api.ui.component.Menu;
import net.rim.device.api.ui.component.NullField;
import net.rim.device.api.ui.container.HorizontalFieldManager;
import net.rim.device.api.ui.container.VerticalFieldManager;

import com.firstBooks.series7.AppConfig;
import com.firstBooks.series7.db.DBMain;
import com.firstBooks.series7.db.Question;
import com.firstBooks.series7.db.parser.XMLParser;
import com.firstBooks.series7.ui.UIinitialize;
import com.firstBooks.series7.ui.managers.TopManager;
import com.vensi.api.ImgButtonField;

public class TestScreen extends ScreenManager implements AppConfig {

    TopManager topManager = null;
    VerticalFieldManager middleManager = null;
    HorizontalFieldManager manager = null;
    ImgButtonField A, B, C, D;
    int quesNumber;
    LabelField question1, blank, choice1Label, choice2Label, choice3Label,
            choice4Label;
    FieldChangeListener checkAnswerListenerA, checkAnswerListenerB,
            checkAnswerListenerC, checkAnswerListenerD;

    public TestScreen() {
        super();
        drawScreen();
    }

    public void drawScreen() {

        topManager = new TopManager(newTestButton, 0);

        middleManager = new VerticalFieldManager(
                VerticalFieldManager.VERTICAL_SCROLL
                        | VerticalFieldManager.VERTICAL_SCROLLBAR
                        | VerticalFieldManager.USE_ALL_WIDTH
                        | Field.FIELD_HCENTER) {
            protected void sublayout(int maxWidth, int maxHeight) {
                // maxwidth reduced by 15 to get padding along the edges
                super.sublayout(maxWidth - 15, maxHeight - 10);

                if (UIinitialize.displayType == Device_Storm) {
                    setExtent(maxWidth - 15, 347);
                } else if (UIinitialize.displayType == Device_Tour) {
                    setExtent(maxWidth - 15, 263);
                } else if (UIinitialize.displayType == Device_Curve) {
                    setExtent(maxWidth - 10, 165);
                }

            }
        };

        A = new ImgButtonField(buttonABkGrndDown, buttonABkGrnd,
                Field.FOCUSABLE | Field.FIELD_HCENTER);
        B = new ImgButtonField(buttonBBkGrndDown, buttonBBkGrnd,
                Field.FOCUSABLE | Field.FIELD_HCENTER);
        C = new ImgButtonField(buttonCBkGrndDown, buttonCBkGrnd,
                Field.FOCUSABLE | Field.FIELD_HCENTER);
        D = new ImgButtonField(buttonDBkGrndDown, buttonDBkGrnd,
                Field.FOCUSABLE | Field.FIELD_HCENTER);


            manager = new HorizontalFieldManager(Manager.NO_HORIZONTAL_SCROLL
                | Manager.NO_VERTICAL_SCROLL | Field.USE_ALL_WIDTH
                | Field.USE_ALL_HEIGHT) {
            protected void sublayout(int maxWidth, int maxHeight) {

                 if (UIinitialize.displayType == Device_Storm) {
                    layoutChild(A, buttonABkGrnd.getWidth(), buttonABkGrnd
                            .getHeight());
                    setPositionChild(A, 25, 9);

                    layoutChild(B, buttonBBkGrnd.getWidth(), buttonBBkGrnd
                            .getHeight());
                    setPositionChild(B, 115, 9);

                    layoutChild(C, buttonCBkGrnd.getWidth(), buttonCBkGrnd
                            .getHeight());
                    setPositionChild(C, 205, 9);

                    layoutChild(D, buttonDBkGrnd.getWidth(), buttonDBkGrnd
                            .getHeight());
                    setPositionChild(D, 295, 9);

                } else if (UIinitialize.displayType == Device_Tour) {
                    layoutChild(A, buttonABkGrnd.getWidth(), buttonABkGrnd
                            .getHeight());
                    setPositionChild(A, 41, 9);

                    layoutChild(B, buttonBBkGrnd.getWidth(), buttonBBkGrnd
                            .getHeight());
                    setPositionChild(B, 161, 9);

                    layoutChild(C, buttonCBkGrnd.getWidth(), buttonCBkGrnd
                            .getHeight());
                    setPositionChild(C, 281, 9);

                    layoutChild(D, buttonDBkGrnd.getWidth(), buttonDBkGrnd
                            .getHeight());
                    setPositionChild(D, 401, 9);
                } else if (UIinitialize.displayType == Device_Curve) {
                    layoutChild(A, buttonABkGrnd.getWidth(), buttonABkGrnd
                            .getHeight());
                    setPositionChild(A, 33, 19);

                    layoutChild(B, buttonBBkGrnd.getWidth(), buttonBBkGrnd
                            .getHeight());
                    setPositionChild(B, 107, 19);

                    layoutChild(C, buttonCBkGrnd.getWidth(), buttonCBkGrnd
                            .getHeight());
                    setPositionChild(C, 182, 19);

                    layoutChild(D, buttonDBkGrnd.getWidth(), buttonDBkGrnd
                            .getHeight());
                    setPositionChild(D, 257, 19);
                }

                setExtent(maxWidth, maxHeight);
            }

            protected void paint(Graphics g) {
                super.paint(g);
            }
        };

        String title = "";

        quesNumber = DBMain.getQuestionNumber();
        System.out.println("the value of QUESNUMBER IS:"+quesNumber);
        DBMain.curQuestion = (Question) XMLParser.questionList
                .elementAt(quesNumber);
        title = DBMain.curQuestion.getTitle();
        System.out.println("the value of TITLE IS:"+title);
        String BlankSpace = "  ";
        String choice1 = "A.  " + DBMain.curQuestion.getChoice1() + "\n" + "  ";
        String choice2 = "B.  " + DBMain.curQuestion.getChoice2() + "\n" + "  ";
        String choice3 = "C.  " + DBMain.curQuestion.getChoice3() + "\n" + "  ";
        String choice4 = "D.  " + DBMain.curQuestion.getChoice4() + "\n" + "  ";

        question1 = new LabelField(title);
        question1.setFont(myFontBoldSmall());

        blank = new LabelField(BlankSpace);
        blank.setFont(myFontBoldSmall());

        choice1Label = new LabelField(choice1);
        choice1Label.setFont(myFontPlainSmall());
        choice2Label = new LabelField(choice2);
        choice2Label.setFont(myFontPlainSmall());
        choice3Label = new LabelField(choice3);
        choice3Label.setFont(myFontPlainSmall());
        choice4Label = new LabelField(choice4);
        choice4Label.setFont(myFontPlainSmall());

        DBMain.answer = DBMain.curQuestion.getAnswer();

        checkAnswerListenerA = new FieldChangeListener() {

            public void fieldChanged(Field field, int context) {
                DBMain.selectedAnswer = "A";
                UiApplication.getUiApplication().pushScreen(new AnswerScreen());
                UiApplication.getUiApplication().popScreen(getScreen());

            }
        };
        A.setChangeListener(checkAnswerListenerA);
        checkAnswerListenerB = new FieldChangeListener() {

            public void fieldChanged(Field field, int context) {
                DBMain.selectedAnswer = "B";
                UiApplication.getUiApplication().pushScreen(new AnswerScreen());
                UiApplication.getUiApplication().popScreen(getScreen());
            }
        };
        B.setChangeListener(checkAnswerListenerB);

        checkAnswerListenerC = new FieldChangeListener() {

            public void fieldChanged(Field field, int context) {
                DBMain.selectedAnswer = "C";
                UiApplication.getUiApplication().pushScreen(new AnswerScreen());
                UiApplication.getUiApplication().popScreen(getScreen());
            }
        };
        C.setChangeListener(checkAnswerListenerC);

        checkAnswerListenerD = new FieldChangeListener() {

            public void fieldChanged(Field field, int context) {
                DBMain.selectedAnswer = "D";
                UiApplication.getUiApplication().pushScreen(new AnswerScreen());
                UiApplication.getUiApplication().popScreen(getScreen());
            }
        };
        D.setChangeListener(checkAnswerListenerD);
        /*A.setChangeListener(checkAnswerListenerA);
        B.setChangeListener(checkAnswerListenerB);
        C.setChangeListener(checkAnswerListenerC);
        D.setChangeListener(checkAnswerListenerD);*/

        manager.add(new NullField(Field.FOCUSABLE));
        manager.add(A);
        manager.add(B);
        manager.add(C);
        manager.add(D);
        manager.add(new NullField(Field.FOCUSABLE));

        middleManager.add(question1);
        middleManager.add(new NullField(Field.FOCUSABLE));
        middleManager.add(blank);
        middleManager.add(choice1Label);
        middleManager.add(new NullField(Field.FOCUSABLE));
        middleManager.add(choice2Label);
        middleManager.add(new NullField(Field.FOCUSABLE));
        middleManager.add(choice3Label);
        middleManager.add(new NullField(Field.FOCUSABLE));
        middleManager.add(choice4Label);

        add(topManager);
        add(middleManager);
        add(manager);
    }

    protected void makeMenu(Menu menu, int instance) {
        menu.add(new MenuItem("A", 20, 10) {
            public void run() {
                answerMenu("A");
            }
        });
        menu.add(new MenuItem("B", 30, 20) {
            public void run() {
                answerMenu("B");
            }
        });
        menu.add(new MenuItem("C", 40, 30) {
            public void run() {
                answerMenu("C");
            }
        });
        menu.add(new MenuItem("D", 50, 40) {
            public void run() {
                answerMenu("D");
            }
        });
        super.makeMenu(menu, instance);
    }

    private void answerMenu(String answer) {
        DBMain.selectedAnswer = answer;

        UiApplication.getUiApplication().pushScreen(new AnswerScreen());
        UiApplication.getUiApplication().popScreen(getScreen());

    }

    protected boolean keyChar(char character, int status, int time) {
        if (character == 'A' || character == 'a')
            DBMain.selectedAnswer = "A";
        else if (character == 'B' || character == 'b')
            DBMain.selectedAnswer = "B";
        else if (character == 'C' || character == 'c')
            DBMain.selectedAnswer = "C";
        else if (character == 'D' || character == 'd')
            DBMain.selectedAnswer = "D";
        else
            return super.keyChar(character, status, time);

        UiApplication.getUiApplication().pushScreen(new AnswerScreen());
        UiApplication.getUiApplication().popScreen(getScreen());
        return true;
    }

    protected void paint(Graphics g) {
        g.drawBitmap(0, 0, UIinitialize.screenWidth, UIinitialize.screenHeight,
                backgroundBitmap, 0, 0);
        subpaint(g);
        TestScreen.this.invalidate();
    }
}

Answer 1

1) Please ask questions in decent English.

2) You might want to take a look at this example. Simply store the questions as question_ID and question_Text in your tables and then put the question_ID's an array, shuffle them and use the shuffled collection to get the questions.