Effective Java

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CHAPTER 9
GENERAL PROGRAMMING
262
postpone the declaration until you do. One exception to this rule concerns 
try
-
catch
statements. If a variable is initialized to an expression whose evaluation can
throw a checked exception, the variable must be initialized inside a 
try
block
(unless the enclosing method can propagate the exception). If the value must be
used outside of the 
try
block, then it must be declared before the 
try
block,
where it cannot yet be “sensibly initialized.” For an example, see page 283.
Loops present a special opportunity to minimize the scope of variables. The
for
loop, in both its traditional and for-each forms, allows you to declare 
loop
variables
, limiting their scope to the exact region where they’re needed. (This
region consists of the body of the loop and the code in parentheses between the
for
keyword and the body.) Therefore, 
prefer 
for
 loops to 
while
 loops
, assum-
ing the contents of the loop variable aren’t needed after the loop terminates.
For example, here is the preferred idiom for iterating over a collection (Item 58):
// Preferred idiom for iterating over a collection or array
for (Element e : c) {
... // Do Something with e
}
If you need access to the iterator, perhaps to call its 
remove
method, the preferred
idiom uses a traditional 
for
loop in place of the for-each loop:
// Idiom for iterating when you need the iterator
for (Iterator i = c.iterator(); i.hasNext(); ) {
Element e = i.next();
... // Do something with e and i
}
To see why these 
for
loops are preferable to a 
while
loop, consider the following
code fragment, which contains two 
while
loops and one bug:
Iterator i = c.iterator();
while (i.hasNext()) {
doSomething(i.next());
}
...
Iterator i2 = c2.iterator();
while (