Check If Two Dimensional Array is empty

Question

I'm working on a class project and hit a roadblock. I've been looking everywhere on how to check if a Two Dimensional Array is empty and if so then it'll continue on with the project. If the array is full then it'll ask the customer to be put on a waiting list. I'm really new to java so if you can please help me out with this! I've been thinking of using a boolean statement but I'm not sure if that'll work. Any case I've written this so far for the array.

char [][] seats = new char [13][6]; //array for row and columns 
for (int row = 0; row < seats.length; row ++) {//output seating to * with no passengers
 for (int col = 0; col < seats[row].length; col ++) {
 seats [row][col] = '*';
 } 
}

• Yep_It's_Me: Is this the code you need help with?
• nem035: @Kerppag that will not work. array.length gives the length of the allocated space, not the number of items actually present
• Ker p pag: ok ok @nem i just tried it and it fails. i guess 2d array should be checked manually?

Answer 1

Judging by your question, you want to take in an array of chars and either:

1. Output true if there is at least one open seat (*)
2. Output false if there isn't.

You want code that looks like this:

public static boolean hasOpenSeat(char[][] seats){
 for(int i = 0; i < seats.length; i++){
 for(int j = 0; j < seats[i].length; j++){
 if(seats[i][j] == '*') 
 return true;
 }
 }
 //Open seat was never found - return false
 return false;
}

Answer 2

It depends on your definition of empty...

You could do a check if each item in the array equals a special value that means "empty" item.

The fastest way to do that is to check item by item, and return false as in "not-empty" as soon as you find a taken seat. If we checked all seats and no taken seats were found then the matrix is empty.

boolean areAllSeatsEmpty(char [][] seats) {
 final char EMPTY_SEAT = '*';
 for (int row = 0; row < seats.length; row ++) {
 for (int col = 0; col < seats[row].length; col ++) {
 if(seats [row][col] != EMPTY_SEAT) { // return false as soon as a non-empty seat is found
 return false;
 }
 }
 }
 return true; // no non-empty seats were found so all seats are empty
}