Java treats each array
element as a variable, which makes it possible to use any arithmetic or
relational operators with arrays elements as operands. To use array elements as operands, we need
to specify the index of the element.
Let’s consider the array numbers from before. We can assign a
new value (say 99) to its first element as follows: numbers[0] = 99; After the above
statement executes, the array will have changed to: numbers
0 1 2 3 4 We can also have 2
array elements as operands in an assignment statement: numbers[2] = numbers[4]; This will copy the
value at index 4, which is 11, to index 2, replacing the 6. The array will be: numbers
0 1 2 3 4 An array index in
Java is not limited to being an integer literal. We can in fact use a variable as an index
into an array as long as the variable is an integer. The following statements are perfectly
valid: int i =
3; System.out.println(numbers[i]); This will print out
the value of the element at index 3 (the fourth element in the array,
8). We can print out the value of the
next element with the statement: System.out.println(numbers[i+1]); // displays the element at index 4 This tells us that we
can index an array using an expression, as long as what the expression inside
the square brackets evaluates to (in this case i+1 is 4) does not exceed the boundaries of the array (0 to 4). Array notation can at
times get confusing when both the index and the array element itself involve
expressions. Consider the statement: numbers[i+1]++; Since i is 3, this is
equivalent to the statement number[4]++, which simply adds one to the
element at index 4. While the value of
the fourth element in the array is changed to 12 (from 11), i’s value remains
the same. |
