Effective Java

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CHAPTER 9
GENERAL PROGRAMMING
290
can be made in favor of capitalizing only the first letter: even if multiple acronyms
occur back-to-back, you can still tell where one word starts and the next word
ends. Which class name would you rather see, 
HTTPURL
or 
HttpUrl
? 
Method and field names follow the same typographical conventions as class
and interface names, except that the first letter of a method or field name should
be lowercase, for example, 
remove
or 
ensureCapacity
. If an acronym occurs as
the first word of a method or field name, it should be lowercase.
The sole exception to the previous rule concerns “constant fields,” whose
names should consist of one or more uppercase words separated by the underscore
character, for example, 
VALUES
or 
NEGATIVE_INFINITY
. A constant field is a static
final field whose value is immutable. If a static final field has a primitive type or
an immutable reference type (Item 17), then it is a constant field. For example,
enum constants are constant fields. If a static final field has a mutable reference
type, it can still be a constant field if the referenced object is immutable. Note that
constant fields constitute the 
only
recommended use of underscores.
Local variable names have similar typographical naming conventions to mem-
ber names, except that abbreviations are permitted, as are individual characters
and short sequences of characters whose meaning depends on the context in which
they occur, for example, 
i
, 
denom
, 
houseNum
. Input parameters are a special kind
of local variable. They should be named much more carefully than ordinary local
variables, as their names are an integral part of their method’s documentation.
Type parameter names usually consist of a single letter. Most commonly it is
one of these five: 
T
for an arbitrary type, 
E
for the element type of a collection, 
K
and 
V
for the key and value types of a map, and 
X
for an exception. The return type
of a function is usually 
R
. A sequence of arbitrary types can be 
T
, 
U
, 
V
or 
T1
, 
T2
, 
T3
.
For quick reference, the following table shows examples of typographical
conventions.