I have a simple int array that is initialize like this:
int [][] tempArray=bp.getArray();//get array from other class(bp)
//doing things with tempArray...
When I change the tempArray it also change the bp.getArray();.
Is this because is it referenced to the bp.getArray();?
Yes, if you want a new reference it's easy, you have to use Arrays.copyOf. Other functions are Array.clone and System.arrayCopy.
Arrays.copyOf// is a Java 6 feature. For older versions switch to System.arrayCopy.
public static int[][] deepCopy(int[][] original) {
if (original == null) {
return null;
}
final int[][] result = new int[original.length][];
for (int i = 0; i < original.length; i++) {
result[i] = Arrays.copyOf(original[i], original[i].length);
}
return result;
}
This will deep copy a 2d array.
The correct answer is, that you need a deep copy. You're assigned references (pointers), rather than assigning values.
Arrays.copyOf() or System.arraycopy() will work -- but only on the bottom level of int[].
At the int[][] level, if you run a copy, you'll get a separate top-level array pointing to the same bottom-level arrays; not a proper deep copy.
To do it properly (at 2 levels):
public int[][] copy2Deep (int[][] src) {
int[][] dest = new int[ src.length][];
for (int i = 0; i < src.length; i++) {
dest[i] = Arrays.copyOf( src[i], src[i].length);
}
return dest;
}
This should work -- the fundamental principle is that int[][] is really an single-dimensional array of int[] with some syntactic sugar added.
Because of this, the bottom dimension is not needed to be known to create the array (it will be filled with 'null' child arrays initially), and src.length can be used to return the length of the top dimension.
See also: Efficient System.arraycopy on multidimensional arrays
Hope this helps.
bp.getArray();is implemented.