reading Array randomly

Question

I've a program & I wont to read ARRAY randomly I don't have error with program but during output I have null value can you give me the solution ...

import java.io.FileInputStream;
import java.util.Properties;
import java.util.Random;
import javax.swing.JOptionPane;

public class ReadDB {
    public static void main(String[] args) {

        Properties prob = new Properties();
        String word [] = new String [20] ;
        try{
            prob.load( new FileInputStream("words.txt"));
        }catch(Exception e){
        }
        for(int i=1; i<6; i++){         
            String temp = prob.getProperty(""+i);
            word[i] = temp;
            Random ran = new Random ();

            String Val = word[ran.nextInt(word.length)];

            System.out.println(Val);

        }
    }
}

FThompson · Accepted Answer · 2012-11-15 21:44:35Z

5

Your array has a length of 20 and you are filling only 5 values: for(int i=1; i<6; i++){. That explains null values.

edited Nov 15, 2012 at 21:44

FThompson

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answered Nov 15, 2012 at 21:40

Samuel Rossille

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Comments

sampson-chen · Accepted Answer · 2012-11-15 21:43:57Z

2

Your array has size 20 but your loop has only 5 iterations.
Your loop starts at the wrong index (partially related)
You are doing the random polling of the word array before it's actually finished being populated with data:

Change it from:

for(int i=1; i<6; i++){         
    String temp = prob.getProperty(""+i);
    word[i] = temp;
    Random ran = new Random ();
    String Val = word[ran.nextInt(word.length)];
    System.out.println(Val);
}

To:

for(int i=0; i<20; i++){         
    String temp = prob.getProperty(""+i);
    word[i] = temp;
}

for(int i=0; i<20; i++){
    Random ran = new Random ();
    String Val = word[ran.nextInt(word.length)];
    System.out.println(Val);
}

answered Nov 15, 2012 at 21:43

sampson-chen

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2 Comments

jangiz Over a year ago

i changed now but a some time i have null but less than before can i use while before second for loop

sampson-chen Over a year ago

@rawaztariq you can try, but as others have pointed out, the bigger issue is how you are actually getting the string for temp.

FThompson · Accepted Answer · 2012-11-15 21:43:08Z

0

Your output could null because prob.getProperty is returning null for the key of the randomly selected index, but more likely the issue is that the randomly generated index is outside the range of 5 values being filled.

Two recommendations:

Never ignore exceptions. Most likely, prob is failing to be loaded due to an exception. Instead, print the exception: e.printStackTrace().
Ensure that your expected properties being loaded actually have the keys 1-5 that you assume exist in filling your words array.

answered Nov 15, 2012 at 21:43

FThompson

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