Arrays are objects which provide space to store up to its size of elements of specified type. An array’s size can not be modified after the array is created.
int[] arr1 = new int[0];
int[] arr2 = new int[2];
int[] arr3 = new int[]{1, 2, 3, 4};
int[] arr4 = {1, 2, 3, 4, 5, 6, 7};
int len1 = arr1.length; // 0
int len2 = arr2.length; // 2
int len3 = arr3.length; // 4
int len4 = arr4.length; // 7The length field in an array stores the size of an array. It is a final field and cannot be modified.
This code shows the difference between the length of an array and amount of objects an array stores.
public static void main(String[] args) {
Integer arr[] = new Integer[] {1,2,3,null,5,null,7,null,null,null,11,null,13};
int arrayLength = arr.length;
int nonEmptyElementsCount = 0;
for (int i=0; i<arrayLength; i++) {
Integer arrElt = arr[i];
if (arrElt != null) {
nonEmptyElementsCount++;
}
}
System.out.println("Array 'arr' has a length of "+arrayLength+"\n"
+ "and it contains "+nonEmptyElementsCount+" non-empty values");
}Result:
Array 'arr' has a length of 13
and it contains 7 non-empty values