Difference between size and length methods?

Question

What is the difference between .size() and .length ? Is .size() only for arraylists and .length only for arrays?

Answer 1

length is constant which is used to find out the array storing capacity not the number of elements in the array

Example:

int[] a = new int[5]

a.length always returns 5, which is called the capacity of an array. But

number of elements in the array is called size

Example:

int[] a = new int[5]
a[0] = 10

Here the size would be 1, but a.length is still 5. Mind that there is no actual property or method called size on an array so you can't just call a.size or a.size() to get the value 1.

The size() method is available for collections, length works with arrays in Java.