Java Reference
In-Depth Information
and a carriage return, respectively. This violates the rule that a string literal cannot be continued in two lines. For
example, in the early stages of compilation "
Hel\u000Alo"
is translated into the following, which is an invalid string
literal and generates a compiler error:
"Hel
lo"
■
it is a compile-time error to use Unicode escapes
\u000A
and
\u000D
in a string literal to represent a line feed
and a carriage return, respectively. You must use the escape sequences of
\n
and
\r
instead.
Tip
What is a CharSequence?
A
CharSequence
is an interface in the
java.lang
package. I discuss interfaces in
Beginning Java Language Features
(ISBN 978-1-4302-6658-7). For now, you can think of a
CharSequence
as an object that represents a readable
sequence of characters.
String
,
StringBuffer
, and
StringBuilder
, to name a few, are instances of
CharSequence
.
They provide read-only methods to read some properties and the content of the sequence of characters represented
by them. In the API documentation for the
String
class, you will see arguments of many methods declared as
CharSequence
. You can always pass a
String
, a
StringBuilder
, or a
StringBuffer
where a
CharSequence
is required.
Creating String Objects
The
String
class contains many constructors that can be used to create a
String
object. The default constructor lets
you create a
String
object with an empty string as its content. For example, the following statement creates an empty
String
object and assigns its reference to the
emptyStr
variable:
String emptyStr = new String();
The
String
class contains a constructor, which takes another
String
object as an argument.
String str1 = new String();
String str2 = new String(str1); // Passing a String as an argument
Now
str1
represents the same sequence of characters as
str2
. At this point, both
str1
and
str2
represent an
empty string. You can also pass a string literal to this constructor.
String str3 = new String("");
String str4 = new String("Have fun!");
After these two statements are executed,
str3
will refer to a
String
object, which has an empty string (a sequence
of zero characters) as its content, and
str4
will refer to a
String
object, which has "
Have fun!"
as its content.
