You are creating an array of zero length (no slots to put anything in)
int array[]={/*nothing in here = array with no slots*/};
and then trying to assign values to array slots (which you don't have, because there are none)
array[i] = number; //array[i] = element i in the array of length 0
You need to define a larger array to fit your needs
int array[] = new int[4]; //Create an array with 4 elements [0],[1],[2] and [3] each containing an int value
You are creating an array of zero length (no slots to put anything in)
int array[]={/*nothing in here = array with no slots*/};
and then trying to assign values to array slots (which you don't have, because there are none)
array[i] = number; //array[i] = element i in the array of length 0
You need to define a larger array to fit your needs
int array[] = new int[4]; //Create an array with 4 elements [0],[1],[2] and [3] each containing an int value
Your code compiles just fine. However, your array initialization line is wrong:
int array[]={};
What this does is declare an array with a size equal to the number of elements in the brackets. Since there is nothing in the brackets, you're saying the size of the array is 0 - this renders the array completely useless, since now it can't store anything.
Instead, you can either initialize the array right in your original line:
int array[] = { 5, 5, 5, 5 };
Or you can declare the size and then populate it:
int array[] = new int[4];
// ...while loop
If you don't know the size of the array ahead of time (for example, if you're reading a file and storing the contents), you should use an ArrayList instead, because that's an array that grows in size dynamically as more elements are added to it (in layman's terms).
Empty Array
Empty an array in Java / processing - Stack Overflow
java - How can I check whether an array is null / empty? - Stack Overflow
FAQ: Learn Java: Arrays - Creating an Empty Array
I recently learnt that an empty array IN JAVA is filled with "0" not null and I was wondering how you will be able to determine the size of the array if you cant say "i != null " how can you tell how many elements are in the array?
There's
Arrays.fill(myArray, null);
Not that it does anything different than you'd do on your own (it just loops through every element and sets it to null). It's not native in that it's pure Java code that performs this, but it is a library function if maybe that's what you meant.
This of course doesn't allow you to resize the array (to zero), if that's what you meant by
"empty". Array sizes are fixed, so if you want the "new" array to have different dimensions you're best to just reassign the reference to a new array as the other answers demonstrate. Better yet, use a List type like an ArrayList which can have variable size.
You can simply assign null to the reference. (This will work for any type of array, not just ints)
int[] arr = new int[]{1, 2, 3, 4};
arr = null;
This will 'clear out' the array. You can also assign a new array to that reference if you like:
int[] arr = new int[]{1, 2, 3, 4};
arr = new int[]{6, 7, 8, 9};
If you are worried about memory leaks, don't be. The garbage collector will clean up any references left by the array.
Another example:
float[] arr = ;// some array that you want to clear
arr = new float[arr.length];
This will create a new float[] initialized to the default value for float.
There's a key difference between a null array and an empty array. This is a test for null.
int arr[] = null;
if (arr == null) {
System.out.println("array is null");
}
"Empty" here has no official meaning. I'm choosing to define empty as having 0 elements:
arr = new int[0];
if (arr.length == 0) {
System.out.println("array is empty");
}
An alternative definition of "empty" is if all the elements are null:
Object arr[] = new Object[10];
boolean empty = true;
for (int i=0; i<arr.length; i++) {
if (arr[i] != null) {
empty = false;
break;
}
}
or
Object arr[] = new Object[10];
boolean empty = true;
for (Object ob : arr) {
if (ob != null) {
empty = false;
break;
}
}
ArrayUtils.isNotEmpty(testArrayName) from the package org.apache.commons.lang3 ensures Array is not null or empty