Does an array object explicitly contain the indexes?

Question

Since day one of learning Java I\'ve been told by various websites and many teachers that arrays are consecutive memory locations which can store the specified number of data al

Answer 1

The critical piece to understand is that memory allocated for an array is contiguous. So given the address of the initial element of an array, i.e., arr[0], this contiguous memory allocation scheme helps the runtime to determine the address of array element given its index.

Say we have declared int[] arr = new int[5], and its initial array element, arr[0], is at address 100. To reach the third element in the array all that the runtime needs to perform is following the math 100 + ((3-1)*32) = 164 (assuming 32 is the size of an integer). So all that the runtime needs is the address of the initial element of that array. It can derive all other addresses of array elements based on the index and the size of the datatype the array stores.

Just an off-topic note: Although the array occupies a contiguous memory location, the addresses are contiguous only in the virtual address space and not in the physical address space. A huge array could span multiple physical pages that may not be contiguous, but the virtual address used by the array will be contiguous. And mapping of a virtual address to a physical address is done by OS page tables.