Lists, Logic, and Loops - Java 6 - page 101

while and do Loops
The remaining types of loops are while and do . As with for loops, while and do loops
enable a block of Java code to be executed repeatedly until a specific condition is met.
Whether you use a for , while , or do loop is mostly a matter of your programming style.

while Loops
The while loop repeats a statement for as long as a particular condition remains true .
Here's an example:

while (i < 13) {
x = x * i++; // the body of the loop

}

The condition that accompanies the while keyword is a Boolean expression— i < 13 in
the preceding example. If the expression returns true , the while loop executes the body
of the loop and then tests the condition again. This process repeats until the condition is
false .

Although the preceding loop uses opening and closing braces to form a block statement,
the braces are not needed because the loop contains only one statement: x = x * i++ .
Using the braces does not create any problems, though, and the braces will be required if
you add another statement inside the loop later.

4

The ArrayCopier application in Listing 4.4 uses a while loop to copy the elements of an
array of integers (in array1 ) to an array of float variables (in array2 ), casting each ele-
ment to a float as it goes. The one catch is that if any of the elements in the first array
is 1, the loop immediately exits at that point.

LISTING 4.4 The Full Text of ArrayCopier.java

1: class ArrayCopier {
2: public static void main(String[] arguments) {
3: int[] array1 = { 7, 4, 8, 1, 4, 1, 4 };
4: float[] array2 = new float[array1.length];
5:
6: System.out.print(“array1: [ “);
7: for (int i = 0; i < array1.length; i++) {
8: System.out.print(array1[i] + “ “);
9: }
10: System.out.println(“]”);
11:
12: System.out.print(“array2: [ “);
13: int count = 0;
14: while ( count < array1.length && array1[count] != 1) {
15: array2[count] = (float) array1[count];