Java array declares as null

I am having trouble with the code specifically with the arrays. I have a while loop set up for the arrays but it's declaring the arrays as null. Do you know what the bug is in my array section?

I'm not sure what do I need to do to fix the null issues in this case. I have went through the code several times and couldn't figure it out.

import java.util.Scanner;
//imports scanner object 
import java.util.Arrays;
//imports scanner object
public class Assignment8_jkaur1240026 {
/**
* @param args the command line arguments
*/
public static void main(String args[]) {
int club_seat = 0;
//creates and initializes club_seat variable
int coach_seat = 5;
//creates and initializies coach_seat variable
int counting_line1 = 0;
//creates and initializes counting1 variable
int counting_line2 = 0;
//creates and initializes counting2 variable
int counting_line3 = 0;
//creates and initializes counting3 variable
boolean reservation = true; 
//boolean used to keep the loop going
Scanner input = new Scanner( System.in );
// create a Scanner object 
do{
System.out.print( "Please specify service class  " );
System.out.println( "(1 = club 2 = coach): ");
//prompt the user to say club or coach seating 
int seating_class = input.nextInt();
//stores the input in seating_class variable 
System.out.println();
//line break
if(seating_class == 1){
//if seating_class var is 1
if(club_seat < 5){
//if club seat is less than 5
club_seat = club(club_seat);
System.out.println("Club Class: Seat # "+ club_seat);
//call the club method and prints it
}
else{
//if club seats are greater than 5
System.out.println("Sorry we are out of club seats");
}
}
else if(seating_class == 2){
//if seating_class var is 1
if(coach_seat < 20){
//if club seat is less than or equal to 20
coach_seat = coach(coach_seat);
System.out.print("Coach Class: Seat # "+ coach_seat);
//call the club method and prints it
}
else{
//if coach seats are greater than 20
System.out.println("Sorry we are out of coach seats");
}
}
else{
System.out.println("Sorry we don't have that service class");
//Say we don't have that class if seating class is not 1 or 2
}
System.out.println();
//line break 
System.out.println("Another reservation (1 = yes 2 = no)? ");
//ask user if they want another reservation 
int another_reservation = input.nextInt();
//store the value inside another reservation int
if(another_reservation == 1){
//if anther reservation is 1
reservation = true;
//keep the boolean reservation as true
}
else if(another_reservation == 2){
//if another reservation is 2
reservation = false;
//change the boolean reservation to false
System.out.println("Have a good day!");
//say bye bye
}
else{
//if another reservation int is not 1 or 2
System.out.println("Sorry we don't understand that command");
//tell the user that they are invalid response
}
System.out.println();
//line break
}
while(reservation == true);
//keep going if reservation is true
String reservation_array_line1[][] = new String [20][1];
while(counting_line1 < 20){
reservation_array_line1[counting_line1][0] = "Seat";
counting_line1 = counting_line1 + 1;
System.out.println(reservation_array_line1[counting_line1][0]);
}
int reservation_array_line2[][] = new int [20][1];
while(counting_line2 < 20){
reservation_array_line2[counting_line2][0] = counting_line2;
counting_line2 = counting_line2 + 1;
System.out.println(reservation_array_line2[counting_line2][0]);
}
String reservation_array_line3[][] = new String [20][1];
while(counting_line3 < 20){
reservation_array_line3[counting_line3][0] = "E";
counting_line3 = counting_line3 + 1;
System.out.println(reservation_array_line3[counting_line3][0]);
}
}
public static int club( int club_seat ){
//method to assign user club seats
club_seat = club_seat + 1;
//increase club_seat by one
return(club_seat);
//return that value
}
public static int coach( int coach_seat ){
//method to assign user coach seats 
coach_seat = coach_seat + 1;
//increase coach_seat by one
return(coach_seat);
//return that value
}
}**

In each loop you increment the index prior to accessing the current element. For example, when counting_line1 is 0 in the first loop, you probably intend to set reservation_array_line1[0][0] to "Seat", print out this value, and then increment counting_line1.

However, because you increment before you access, you actually print out reservation_array_line1[1][0], which hasn't been set to anything except its default value, null, because that's what the next iteration of your loop is supposed to take care of. In fact, you will notice an ArrayIndexOutOfBoundsException on the last iteration of your loop when a non-existent element, reservation_array_line1[20][0], attempts to be accessed.

To fix it, simply swap the order in which you increment and access:

    String reservation_array_line1[][] = new String [20][1];
    while(counting_line1 < 20){
        reservation_array_line1[counting_line1][0] = "Seat";
        System.out.println(reservation_array_line1[counting_line1][0]);
        counting_line1 = counting_line1 + 1;
    }
    int reservation_array_line2[][] = new int [20][1];
    while(counting_line2 < 20){
        reservation_array_line2[counting_line2][0] = counting_line2;
        System.out.println(reservation_array_line2[counting_line2][0]);
        counting_line2 = counting_line2 + 1;
    }
    String reservation_array_line3[][] = new String [20][1];
    while(counting_line3 < 20){
        reservation_array_line3[counting_line3][0] = "E";
        System.out.println(reservation_array_line3[counting_line3][0]);
        counting_line3 = counting_line3 + 1;
    }