Java Reference
In-Depth Information
The Enhanced for Loop
Relatively recently, a new form of the
for
loop, called the
enhanced
for
, was added to Java.
The enhanced
for
provides a streamlined way to cycle through the contents of a collection
of objects, such as an array. The enhanced
for
loop is discussed in
Chapter 5
, after arrays
have been introduced.
The while Loop
Another of Java's loops is the
while
. The general form of the
while
loop is
while
(condition) statement
;
where
statement
may be a single statement or a block of statements, and
condition
defines
the condition that controls the loop. The condition may be any valid Boolean expression.
The loop repeats while the condition is true. When the condition becomes false, program
control passes to the line immediately following the loop.
Here is a simple example in which a
while
is used to print the alphabet:
Here,
ch
is initialized to the letter a. Each time through the loop,
ch
is output and then in-
cremented. This process continues until
ch
is greater than z.
As with the
for
loop, the
while
checks the conditional expression at the top of the loop,
which means that the loop code may not execute at all. This eliminates the need for per-
forming a separate test before the loop. The following program illustrates this characteristic
of the
while
loop. It computes the integer powers of 2, from 0 to 9.
