Java Reference
In-Depth Information
consolenextInt
becomes a new identifier. If you used
consolenextInt
in a program,
the compiler (could) generate an undeclared identifier syntax error. Similarly, omitting
the parentheses, as in
console.nextInt
, also results in a syntax error.
Usually, several methods and/or variables are associated with a particular
class
,each
doing a specific job. In the dot notation, the dot separates the
class
variable name,
that is, the object name from the member, or method, name. It is also worth noting
that
methods
are distinguished from (reference) variables by the presence of parentheses, and
methods that have no parameters must have empty parentheses (like in
nextInt()
). For
example,
console
is the name of a (reference) variable, and
nextInt
is the name of
amethod.
3
class String
This section explains how to use
String
methods to manipulate strings. First, we review
some terminology that we typically use while working with strings and the
class
String
.
Consider the following statements:
String name;
//Line 1
name = "Lisa Johnson";
//Line 2
The statement in Line 1 declares
name
to be a
String
variable. The statement in Line 2
creates the string
"Lisa Johnson"
and assigns it to
name
.
In the statement in Line 2, we usually say that the
String
object, or the string
"Lisa
Johnson"
, is assigned to the
String
variable or the variable
name
. In reality, as explained
before, a
String
object with the value
"Lisa Johnson"
is instantiated (if it has not
already been created) and the address of the object is stored in
name
. Whenever we
use the term ''the string
name
'', we are referring to the object containing the string
"Lisa Johnson"
. Similarly, when we use the terms (reference) variable
name
or
String
variable
name
, we simply mean
name
, whose value is an address.
The remainder of this section describes various features of the
class
String
. In Chapter
2, you learned that two strings can be joined using the operator +. The
class
String
provides various methods that allow us to process strings in various ways. For example,
we can find the length of a string, extract part of a string, find the position of a particular
string in another string, convert a number into a string, and convert a numeric string into
a number.
Each method associated with the
class
String
implements a specific operation and has
a specific name. For example, the method for determining the length of a string is named
length
, and the method for extracting a string from within another string is named
substring
.
As explained in the earlier section, Using Predefined Classes and Methods in a Program,
in general, to use a method you must know the name of the
class
containing the
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