StackOverflow2013

Note that there are some explanatory texts on larger screens.

plurals

POWhy do I get a NullPointerException when using text input as opposed to user input?
text
Body
copied!<p>So I have to write a program that is a flight reservation system. If I run the program normally and enter in values when prompted, nothing goes wrong, but when I use a .txt file input, I get a <code>NullPointerException</code>. The part of the code im getting the <code>NullPointerException</code> is </p> <pre><code> public void instantiateAirplane() throws IOException{ boolean creatingAirplane = true; String className= ""; String seatFormat; int rowNums; while (creatingAirplane){ input = new BufferedReader(new InputStreamReader(System.in)); System.out.println("Enter service class name or [ENTER] to finish: "); className = input.readLine(); if (className.equals("")) { creatingAirplane = false; } else{ System.out.println("Enter seating pattern: "); seatFormat = input.readLine(); System.out.println("Enter number of rows: "); rowNums = Integer.parseInt(input.readLine()); plane.creatSeatingChart(className, rowNums, seatFormat); } } } </code></pre> <p>When doing normal input, it runs like this:</p> <pre><code>C:\Users\Owner\Desktop\Math&CIS\CS151\HW1>java UserInterface planes Enter service class name or [ENTER] to finish: First Class Enter seating pattern: WAAW Enter number of rows: 2 Enter service class name or [ENTER] to finish: Business Class Enter seating pattern: WAAW Enter number of rows: 2 Enter service class name or [ENTER] to finish: Add [P]assenger, Add [G]roup, [C]ancel Reservations, Print [S]eating chart, Prin t [M]anifest, [Q]uit </code></pre> <p>But when when using a .txt input, the following happens </p> <pre><code>C:\Users\Owner\Desktop\Math&CIS\CS151\HW1>java UserInterface planes < input.txt Enter service class name or [ENTER] to finish: Enter seating pattern: Enter number of rows: Enter service class name or [ENTER] to finish: Exception in thread "main" java.lang.NullPointerException at UserInterface.instantiateAirplane(UserInterface.java:21) at UserInterface.main(UserInterface.java:123) C:\Users\Owner\Desktop\Math&CIS\CS151\HW1> </code></pre> <p>the exception happens at the line "<code>if (className.equals("")) {</code>"</p> <p>the input text is the follwing:</p> <pre><code>First WAAW 2 Economy WCAACW 3 ... </code></pre> <p>I'm not sure why it doesn't work when using an input text.</p>

Querying!

Guidance

An individual column

Larger individual text columns get their own page to allow for proper reading.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload