Java Modifying Elements in a foreach
I'm learning Java on my own; and therefore the code below has no function other than for learning/testing.
Essentially I'm trying to modify the elements of an Integer array (namely, halving them) whilst in a foreach loop.
I should note that I'm not re-ordering, adding, or deleting elements; simply changing their values.
Here is my code:
Logger.describe("Now copying half of that array in to a new array, and halving each element");
Integer[] copyArray = new Integer[DEFAULT_SAMPLE_SIZE / 2];
System.arraycopy(intArray, 0, copyArray, 0, DEFAULT_SAMPLE_SIZE / 2);
for (Integer x : copyArray) x /= 2;
Logger.output(Arrays.deepToString(copyArray));
However, the original array (intArray) is this:
[47, 31, 71, 76, 78, 94, 66, 47, 73, 21]
And the output of copyArray is:
[47, 31, 71, 76, 78]
So although the array has been halved in size, the elements (Integers) haven't also been halved in value. So what am I doing wrong?
Thank you
You can't do that in a foreach loop.
for (int i=0; i<copyArray.length;i++)
copyArray[i] /= 2;
Else you are not assigning it back into the array. Integer
objects are immutable by the way so can't modify them (creating new ones though).
Updated from comment: Beware though that there are a few things going on, autoboxing/unboxing for example, roughly:
copyArray[i] = Integer.valueOf(copyArray[i].intValue()/2);
for (int i = 0; i< copyArray.length; i++) {
copyArray[i] = new Integer(x /2);
}
should work.
int counter = 0;
for(int x : copyArray)
{
x /= 2;
copyArray[counter++] = x;
}
Your program just modified the value of variable x
, not the values within the blocks of array copyArray