Java array beginner confusion

Question

Basically I would like to store information about a train within arrays. I believe I would need to use a 2d array. I can't seem to get it working correctly. I want an array that will let me keep track of the number of empty and reserved seats on each car of a train. Is this going to work for me?

    int[][] seats = new int[4][10]; 
    for (int row = 0; row < 4; row ++)
        for (int col = 0; col < 10; col++)
            car[row][col] = 0;

I want for this just to initialize all the seats to 0, signifying they are empty. I currently get an error message on the semi colon after int[4][10], it says "expected , {"

It's less about arrays and more about your code formatting. It says it's expected a {, add some {'s to your code. — Russell Shingleton
– Russell Shingleton, Commented Dec 12, 2013 at 19:37

user180100 · Accepted Answer · 2013-12-12 19:37:43Z

4

Your code is valid, the only error is that car should be seats:

int[][] seats = new int[4][10]; 
for (int row = 0; row < 4; row++)
   for (int col = 0; col < 10; col++)
      seats[row][col] = 0;

answered Dec 12, 2013 at 19:37

user180100

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1 Comment

user180100 Over a year ago

Maybe your IDE is misleading you, try to restart it (clearing the project might also help)

Bob Kuhar · Accepted Answer · 2013-12-13 00:27:13Z

2

Well your first problem is that you have an array named "seats" but you are trying to initialize something called "car". Nesting for loops like that without including the '{', '}' to delimit them is, at least, bad style, and maybe has the compiler confused? The following works like a champ for me.

int[][] seats = new int[4][10];
for ( int rowIx = 0; rowIx < seats.length; rowIx++ ) {
    for ( int colIx = 0; colIx < seats[rowIx].length; colIx++ ) {
        seats[rowIx][colIx] = 0;
    }
}

...although it works equally well without the squigglies but I find that much harder to read. I also think you should get in the habit of asking the array its length rather than assuming fixed size. Thats what is going on in the seats.length and seats[rowIx].length calls.

edited Dec 13, 2013 at 0:27

answered Dec 12, 2013 at 19:40

Bob Kuhar

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Comments

Brian Dishaw · Accepted Answer · 2013-12-12 20:06:03Z

1

Give this a try and see if it helps. I think the IDE is looking for initialization syntax since that's what you are doing in the loops. I could be mistaken on exactly what's going on but the code will compile for you.

int[][] seats = new int[4][10];
{
    for (int row = 0; row < 4; row++) {
        for (int col = 0; col < 10; col++) {
            seats[row][col] = 0;
        }
    }
}

edited Dec 12, 2013 at 20:06

answered Dec 12, 2013 at 20:00

Brian Dishaw

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Comments

clcto · Accepted Answer · 2013-12-12 19:41:17Z

0

Use a basic class to store the information.

class TrainCar
{
     private int _emptySeats;
     private int _totalSeats;

     public TrainCar( int total )
     {
         _totalSeats = total;
         _emptySeats = total;
     }

     public bool fillSeats( int num )
     {
         _emptySeats -= num;
         if( _emptySeats < 0 )
         {
             _emptySeats += num;
             return false;
         }
         return true;
     }

     public int getFilledSeats()
     {
         return _totalSeats - _emptySeats;
     }

     public int getEmptySeats()
     {
         return _emptySeats;
     }
}

And then just use an array (or ArrayList) of the TrainCar class

TrainCar[] cars = new TrainCar[ NUM_CARS ];
for( int i = 0; i < cars.length; ++i )
    cars[i] = new TrainCar( SEATS_PER_TRAINCAR );

answered Dec 12, 2013 at 19:41

clcto

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1 Comment

user2884621 Over a year ago

I would do this, but this is for an Android app. I need the values to be passed and manipulated between different activities. From what I have learned today, SharedPreferences is the way for me to do this, but only allows me to use primitive data types.

Chris1992 · Accepted Answer · 2013-12-12 20:53:22Z

0

In the fourth line, car needs to be replaced with seats. It is also good form to keep track of loops with { }, even for single lines.

int[][] seats = new int[4][10]; 
for (int row = 0; row < 4; row ++)
{
    for (int col = 0; col < 10; col++)
    {
        seats[row][col] = 0;
    }
}

answered Dec 12, 2013 at 20:53

Chris1992

1

Comments

JCLL · Accepted Answer · 2013-12-12 19:41:16Z

-1

The syntax of the loop statement is not respected here : braces are needed !

tutorial explaining the syntax

answered Dec 12, 2013 at 19:41

JCLL

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