CODEWITHSUNDEEP
java
Leo Jiang
Leo Jiang

Reputation: 26085

How do I check if an array element exists?

I'm looking for Java's equivalent of PHP's isset();

int board[][]=new int[8][8];
...
if(isset(board[y][x]))
  // Do something with board[y][x]

Does such a function exist in Java?

Edit: Sorry, what I meant is that I want to check if board[100][100] exists or not. if(board[100][100]) would result in an array out of bounds error.

Upvotes: 4

Views: 17398

Answers (5)

Jeffrey Blattman
Jeffrey Blattman

Reputation: 22637

In Java, int arrays are initialized to a value of zero, so you won't be able to tell if it's been not set, or if it's set to a value of 0.

If you want to check if it's set, you should use an array of Integer. If the value isn't set, it will be null.

Integer[][] board = new Integer[8][8];
...
if (board[x][y] != null) { ... }

Upvotes: 6

Mike McMahon
Mike McMahon

Reputation: 8594

  if (board[x][y] != null) {
    // it's not null, but that doesn't mean it's "set" either.  You may want to do further checking to ensure the object or primitive data here is valid
  }

Java doesn't have an equiv. to isset because knowing if something is truly set goes beyond just stuffing a value into a location.

Upvotes: -1

TofuBeer
TofuBeer

Reputation: 61526

Probably better to not use int, you could use Integer if you really have to have it as an int, but generally speaking a complex object is going to be better (like a ChessPiece or something). That way you can check to see if the value == null (null means it has not been set).

Upvotes: 0

Kevin Bowersox
Kevin Bowersox

Reputation: 94429

I think a basic null check would work.

String[] myArray = {"Item1", "Item2"};

for(int x =0; x < myArray.length; x++){
    if(myArray[0] != null)
    {
      ...do something
    }
}

Upvotes: 1

OnResolve
OnResolve

Reputation: 4032

You can create a method that checks that first the x, y is in the bounds of the array and if it is that the value is not null. I don't believe there is a built in method for array, but there are helper functions similar like .contains() for ArrayLists.

Upvotes: 0

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