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POWhy do I get a NullPointerException when using text input as opposed to user input?
 

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  1. POWhy do I get a NullPointerException when using text input as opposed to user input?
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    <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&amp;CIS\CS151\HW1&gt;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&amp;CIS\CS151\HW1&gt;java UserInterface planes &lt; 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&amp;CIS\CS151\HW1&gt; </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>
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    1. COCan you confirm that has your code `if (className.equals("")) {` this statement at `line 21` in `UserInterface.java` ?
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      1. POWhy do I get a NullPointerException when using text input as opposed to user input?
      1. USMohamed Saligh
 

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