java arrays printing as null

Question

Hello, i am making a alarm program and i am having trouble with gathering data from the db.txt file i tried to do System.out.println(array[]); but it didn't do anything i was wondering if it is possible to create an int lets call it number and use it to choose an array to print like this System.out.println(array[number]); anyways thats what i was trying to do and it still returned null. Here is my java cod:

import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;
import javax.swing.*;

public class alarm {
public static JFrame window;
public JPanel p;
public RandomAccessFile rw;
    alarm() throws IOException {
        window = new JFrame();
        window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        window.setResizable(false);
        window.setSize(600, 600);
        p = new JPanel();
        p.setLayout(null);
        try {
            rw = new RandomAccessFile("db.txt", "rw");
            int loop = 0;
            int insertNumber = 0;
            int[] numberArray = new int[1000000];
            String[] name = new String[1000000];
            String[] desc = new String[1000000];
            String[] date = new String[1000000];
            String row = null;
            while(loop == 0) {
                 row = rw.readLine();
                 if(row == "/") {
                    insertNumber = insertNumber + 1;
                    insertNumber = numberArray[insertNumber];
                    name[insertNumber] = rw.readLine();
                    desc[insertNumber] = rw.readLine();
                    date[insertNumber] = rw.readLine();
                }
               if(row == null) {
                    insertNumber = 0;
                    loop = 1;   
                }
        }
        System.out.println("Arrays loaded");
            while(loop == 1) {
            insertNumber = insertNumber + 1;
            if(name[insertNumber] == null) {
                loop = 2;
            }
            System.out.println(name[insertNumber]);
        } 
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    }
}
public static void main(String[] args) throws IOException {
    new alarm();
    window.setVisible(true);
}

}

Possible duplicate of [What is a Null Pointer Exception, and how do I fix it?](http://stackoverflow.com/questions/218384/what-is-a-null-pointer-exception-and-how-do-i-fix-it) — redFIVE, Nov 23 '15 at 23:44
As a matter of good practice, you should check if `row` is null before you do any other comparisons (since the other comparisons would not be true if the null check fails) — blurfus, Nov 23 '15 at 23:48

Don Scott · Answer 1 · 2015-11-24T01:05:01.393

1

You increment index insertNumber to the next value, which is null in the array, then you print it.

while(loop == 1) {
     insertNumber = insertNumber + 1; // insertNumber is incr. before index 0 is printed
     if(name[insertNumber] == null) {  // Always true if size < 2 elements
        loop = 2;
     }
     System.out.println(name[insertNumber]); //prints null is size < 2
}

Try instead:

for(String element : name) {
     System.out.println(element + " ");
}

Additionally, this line is incorrect:

insertNumber = numberArray[insertNumber];

edited Nov 24 '15 at 01:05

answered Nov 23 '15 at 23:50

Don Scott

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@TotZam Look at the second loop... `insertNumber = insertNumber + 1;` (Search it.) – Don Scott Nov 23 '15 at 23:56
1

Is there a reason for the downvote? This is the correct answer. – Don Scott Nov 24 '15 at 01:03

java arrays printing as null

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