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copied!<p>I'm writing a simple class to simulate an airplane reservation system. Unfortunately, I keep having my plan-to-hog-all-first-class-seats glee interrupted by multiple null pointer exceptions, and I can't find them anywhere. Here is my completed work:</p> <pre><code>import java.util.*; public class airplane { boolean[] seats; Scanner scan = new Scanner(System.in); public airplane(int num_of_seats) { boolean[] seats = new boolean[num_of_seats]; for (int counter = 0; counter < num_of_seats; counter++) { seats[counter] = true; } } public boolean seatFirstClass(int seat) { if ( seat <= seats.length / 4 ) return true; else return false; } public void seatsReserveFirstClass() { for (int seat = 0; seat < seats.length; seat++) { if (seats[seat] == true && seat <= seats.length / 4) { seats[seat] = false; System.out.print("I have reserved one seat in first class. Please tell the passenger to enjoy their flight with these airlines! "); break; } } System.out.print("I could not find a seat in first class. Can the passenger switch to economy? (0 for no, 1 for yes) "); int choice = scan.nextInt(); if (choice == 0) System.out.print("I could not add passenger due to lack of a seat."); else if (choice == 1) { this.seatsReserveEconomy(); } } public void seatsReserveEconomy() { for (int seat = 0; seat < seats.length; seat++) { if (seats[seat] == true && seat > seats.length / 4) { seats[seat] = false; System.out.print("I have reserved a seat in economy. Please tell the passenger to enjoy their flight with these airlines! "); break; } } System.out.print("I could not find a seat in economy. Can the passenger switch to first class? (0 for no, 1 for yes) "); int choice = scan.nextInt(); if (choice == 0) System.out.print("I could not add the passenger due to a lack of seats."); else if (choice == 1) this.seatsReserveFirstClass(); } public void planeClear() { for (int seat = 0; seat < seats.length; seat++) { seats[seat] = true; } } public void seatUnReserve(int seat) { if (seat < seats.length) { if (seats[seat] == false) { seats[seat] = true; System.out.printf("Seat %d has been unreserved.\n", seat); } else { System.out.print("The seat you have entered is already unreserved.\n"); } } else { System.out.printf("There is no seat number %d on this plane.\n", seat); } } } </code></pre> <p>and here is a main class to test it:</p> <pre><code>public class Test { public static void main(String[] args) { Scanner scan = new Scanner(System.in); boolean check = false; System.out.print("How many seats does the plane have? "); int num_of_seats = scan.nextInt(); airplane Airplane = new airplane(num_of_seats); while (check == false) { System.out.print("Please enter 0 to reserve a first class seat, 1 to reserve an economy seat,\n2 to cancel a reservation, 3 to clear the plane,\nand 4 to quit the program. "); int choice = scan.nextInt(); switch(choice) { case 0: Airplane.seatsReserveFirstClass(); break; case 1: Airplane.seatsReserveEconomy(); break; case 2: System.out.print("Which seat should I unreserve? "); int seat = scan.nextInt(); Airplane.seatUnReserve(seat); break; case 3: Airplane.planeClear(); break; case 4: check = true; break; } } } } </code></pre> <p>If this is run, the dreaded NullPointException error shows up, and I'm not sure what calls this beast.</p> <pre><code>Exception in thread "main" java.lang.NullPointerException at airplane.seatsReserveFirstClass(airplane.java:22) at Test.main(Test.java:15) </code></pre>

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