- From CS170, you learned that:
- An array is
a series of
variables
- Each variable (called array element) has the same data type
If A[ ] is a one-dimensional array, then A[i] denotes the ith-element in the array A[ ]
- An array is
a series of
variables
- Java provides
array bound checks as
a built-in service to
prevent the (Java) program to
access non-existing array elements
- Array bound checks is
not a
common practice because:
- Array bound check will slow down the program execution !!!
Each time an array element is used in the program, a small piece of array bound check program code fragment is run.
The array bound check execution can slow down the program considerably.
That's why most programming languages do not provide array bound check by default.
In some languages, you can request the compiler to add array bound check when you develop the program).
- We will not perform
array bound check when
we write code to
access array elements
Adding array bound check codes in assembler will make the assembler program extremely complex.
- The elements of an
array are
stored contiguously
in memory:
- You can define arrays of
different data types, such as
byte arrays,
short arrays and
integer arrays
Since each data type uses a different number bytes to store their values, consequently:
- Array elements of differently typed array will use different number of bytes to store each array element
Specifically:
- A byte (typed) array uses 1 byte to store each of its array element
- A short (typed) array uses 2 bytes to store each of its array element
- A int (typed) array uses 4 bytes to store each of its array element
- This is how a
byte typed array is stored
in memory:
Each array element is stored in 1 byte of memory
The array elements are stored in contiguous memory
- This is how a
short typed array is stored
in memory:
Each array element is stored in 2 bytes of memory
The array elements are stored in contiguous memory
- This is how a
int typed array is stored
in memory:
Each array element is stored in 4 bytes of memory
The array elements are stored in contiguous memory