Most of the time, if you are using a single character value, you will use the primitivechar
type. There are times, however, when you need to use a char as an object—for example, as a method argument where an object is expected. The Java programming language provides a wrapper class that "wraps" thechar
in aCharacter
object for this purpose. An object of typeCharacter
contains a single field whose type ischar
. ThisCharacter
class also offers a number of useful class (i.e., static) methods for manipulating characters.Strings are a sequence of characters and are widely used in Java programming. In the Java programming language, strings are objects. The
String
class has over 60 methods and 13 constructors.Most commonly, you create a string with a statement like
rather than using one of theString s = "Hello world!";String
constructors.The
String
class has many methods to find and retrieve substrings; these can then be easily reassembled into new strings using the+
concatenation operator.The
String
class also includes a number of utility methods, among themsplit()
,toLowerCase()
,toUpperCase()
, andvalueOf()
. The latter method is indispensable in converting user input strings to numbers. TheNumber
subclasses also have methods for converting strings to numbers and vice versa.In addition to the
String
class, there is also aStringBuilder
class. Working withStringBuilder
objects can sometimes be more efficient than working with strings. TheStringBuilder
class offers a few methods that can be useful for strings, among themreverse()
. In general, however, theString
class has a wider variety of methods.A string can be converted to a string builder using a
StringBuilder
constructor. A string builder can be converted to a string with thetoString()
method.