Arrays and ArrayLists - Java: How to Program Early Objects - page 262

7.7 Enhanced for Statement
The enhanced for statement iterates through the elements of an array without using a
counter, thus avoiding the possibility of “stepping outside” the array. We show how to use
the enhanced for statement with the Java API's prebuilt data structures (called collections)
in Section 7.16. The syntax of an enhanced for statement is:

for ( parameter : arrayName )
statement

where parameter has a type and an identifier (e.g., int number ), and arrayName is the array
through which to iterate. The type of the parameter must be consistent with the type of the
elements in the array. As the next example illustrates, the identifier represents successive
element values in the array on successive iterations of the loop.
Figure 7.12 uses the enhanced for statement (lines 12-13) to sum the integers in an
array of student grades. The enhanced for 's parameter is of type int , because array con-
tains int values—the loop selects one int value from the array during each iteration. The
enhanced for statement iterates through successive values in the array one by one. The
statement's header can be read as “for each iteration, assign the next element of array to
int variable number , then execute the following statement.” Thus, for each iteration, iden-
tifier number represents an int value in array . Lines 12-13 are equivalent to the following
counter-controlled repetition used in lines 12-13 of Fig. 7.5 to total the integers in array ,
except that counter cannot be accessed in the enhanced for statement:

for ( int counter = 0 ; counter < array.length; counter++)
total += array[counter];

1 // Fig. 7.12: EnhancedForTest.java

2 // Using the enhanced for statement to total integers in an array.

3
4 public class EnhancedForTest

5 {

6 public static void main(String[] args)

7 {

8 int [] array = { 87 , 68 , 94 , 100 , 83 , 78 , 85 , 91 , 76 , 87 };

9 int total = 0 ;

10
11 // add each element's value to total

for ( int number : array)
total += number;

12

13

14
15 System.out.printf( "Total of array elements: %d%n" , total);

16 }

17 } // end class EnhancedForTest

Total of array elements: 849
Fig. 7.12 | Using the enhanced for statement to total integers in an array.

The enhanced for statement can be used only to obtain array elements—it cannot be
used to modify elements. If your program needs to modify elements, use the traditional
counter-controlled for statement.