textfile with Java problems

[saytri]

I am making a quiz, and i wrote the questions in a textfile. But i wish that the questions when they are called from Java come up randomly, not always in the same state. What can i do? Thanks a lot for the help. :)

[tim]

Hi!. Here's a method that will read a text file:

public static Vector<String> loadFile(String filename){
    Vector<String> strings = new Vector<String>();
    try{
        FileReader file = new FileReader(filename);
        BufferedReader buffer = new BufferedReader(file);
        while (true)
        {
            String line = buffer.readLine();
            if (line == null)
                break;
            else {
                strings.add(line); 
            }
        }
        buffer.close();
    } catch (Exception e) {
        System.out.println("Error: " + e.getMessage());
    }
    return strings;
}

Using this method and Math.random(), you can access random lines in your text file. Lets assume that each question is on a separate line in the text file. Your main() method could look like this.

public static void main(String[] arguments){
    Vector<String> data = loadFile("questions.txt");
    int pos = (int)((double)data.size() * Math.random());
    System.out.println("Next question: " + data.get(pos));
}

Remember to add the imports:

import java.io.*;
import java.util.*;

My code has been checked by hand, so just scream if there is a problem. ;)

[saytri]

Thanks a lot for your help. :-) But i have already written the piece of code where i read the file, and since its a bit differnet from yours, i got a bit confused oh how to implement the Math.random() into my piece of code. Can you pls help me do the method Math.random into my piece of code, because i got confused. Thanks a lot. I appreciate a lot your help. :-)

This is the code i have written:

import java.awt.*;
import java.awt.event.*;
import java.util.*;
import java.io.*;
import javax.swing.*;
 
public class GQ extends JFrame implements ActionListener {
    private static final int FRAME_WIDTH = 140;
    private static final int FRAME_HEIGHT = 160;
    private static final int FRAME_X_ORIGIN = 70;
    private static final int FRAME_Y_ORIGIN = 50;
    AnswerStore answerStore = new AnswerStore();
 
    
    public static void main (String[] args) {
        
        
       

        JOptionPane.showMessageDialog(null, "This is a Geography Quiz");
        JOptionPane.showMessageDialog(null, "Good Luck");
 
        
 
            GQ frame = new GQ();
            frame.setVisible(true);
       
    }
 
    public GQ() {
        Container contentPane;
        JButton button1, button2, button3, button4, button5;
 
        setSize (FRAME_WIDTH, FRAME_HEIGHT);
        setTitle("Geography Quiz");
        setLocation(FRAME_X_ORIGIN, FRAME_Y_ORIGIN);
 
        contentPane = getContentPane();
        contentPane.setBackground(Color.pink);
        contentPane.setLayout(new FlowLayout());
 
        button1 = new JButton("Plate Tectonics");
        button2 = new JButton("Rivers");
        button3 = new JButton("Rocks");
        button4 = new JButton("Quit");
 
        contentPane.add(button1);
        contentPane.add(button2);
        contentPane.add(button3);
        contentPane.add(button4);
    
        button1.addActionListener(this);
        button1.setActionCommand("b1");
        button2.addActionListener(this);
        button2.setActionCommand("b2");
        button3.addActionListener(this);
        button3.setActionCommand("b3");
        button4.addActionListener(this);
        button4.setActionCommand("b4");
        setDefaultCloseOperation(EXIT_ON_CLOSE);
    }
  
     public void actionPerformed(ActionEvent e) {
        String ac = e.getActionCommand();
        String[] questions = null;
        String[] answers = null;
        if (ac.equals("b1")) {
            questions = readFile("plate_tectonics.txt");
          
            answers = answerStore.tectonicAnswers;
             
        } else if(ac.equals("b2")) {
            questions = readFile("rivers.txt");
            answers = answerStore.riverAnswers;
        } else if(ac.equals("b3")) {
            questions = readFile("rocks.txt");
            answers = answerStore.rockAnswers;
        } else if (ac.equals("b4")) {
            System.exit(0);
        }
        askQuestions(questions, answers);
    }
       
    
    
    
 
    private String[] readFile(String path) {
        Scanner s = null;
        StringBuilder sb = new StringBuilder();
        String separator = "\n";
        try {
            s = new Scanner(new BufferedReader(new FileReader(path)));
//            s.useDelimiter(",\\s*");
            while (s.hasNext()) {
                sb.append(s.nextLine() + separator);
//                JOptionPane.showMessageDialog(null,s.next());
            }
        } catch(IOException e) {
            System.out.println("read error: " + e.getMessage());
        } finally {
            if (s != null) 
                s.close();
//            break;
        }
        
        System.out.println("sb = " + sb.toString());
        System.out.printf("sb.split = %s%n", Arrays.toString(sb.toString().split("\\n")));
        return sb.toString().split("\\n");
    }
 
    private void askQuestions(String[] questions, String[] answers) {
        
        System.out.printf("questions = %s%nanswers = %s%n",
                           Arrays.toString(questions),
                           Arrays.toString(answers));
        int count = 0;
        int point = 0;
        for(int j = 0; j < questions.length; j++) {
            String input = JOptionPane.showInputDialog(null, questions[j]);
            if(answers[j].equals(input))
              { 
                count++;
                point++;
            }   
            }
            JOptionPane.showMessageDialog(null, "You answered " + count +
                                      " out of " + questions.length +
                                      " questions correctly.");
            JOptionPane.showMessageDialog(null, "Your Geography Quiz score is " + ((point*100)/10) + " % ");
        
          if(point>=0 && point<=3)
          {
             
              JOptionPane.showMessageDialog(null, "You need to Improve");
           }
           
           
         if(point>=4 && point<=7)
          {
             
              JOptionPane.showMessageDialog(null, "Good");
           }
           
           if(point>=8 && point<=10)
          {
             
              JOptionPane.showMessageDialog(null, "You did Great");
           }
                                    
      }
    }
 
class AnswerStore  {
    String[] tectonicAnswers = {
        "Hellenic", "destructive", "100km", "Italy", "Wegner",
        "Mariana", "Sicily", "created", "constructive", "Mediterranean"
    };
    
    String[] riverAnswers = {
        "Gorges", "Meanders", "Levees", "Yes", "Less Economic Developed Countries",
        "crescent shaped lakes", "More Economic Developed Countries", "No", "River Discharge", "No"
    };
    
    String[] rockAnswers = {
        "40km", "Igneous Rock", "Sedimentary", "Basalt", "Organic",
        "pressure", "Oolites", "Igneous", "dark black", "basalt"
    };

 

}

Thanks again :)

[tim]

Let's create a mix method:

    public static String[] mix(String[] array){
        Vector<String> data = new Vector<String>();
        String[] result = new String[array.length];
        for (String string : array)
            data.add(string);
        int count = 0;
        while (data.size() > 0){
            int pos = (int)(Math.random() * (double)data.size());
            String next = data.get(pos);
            result[count++] = next;
            data.remove(pos);
        }
        return result;
    }

Use this method to mix the array before you use it:

questions = mix(questions);

[saytri]

Ok thanks a lot. Happy New Year! :-)