Summary of Characters and Strings
Most of the time, if you are using a single character value, you will use the primitive
char 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" the
char in a
Character object for this purpose. An object of type
Character contains a single field whose type is
char . This Character 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
String s = "Hello world!";
rather than using one of the
String class has many methods to find and retrieve substrings; these can then be easily reassembled into new strings using the
+ concatenation operator.
String class also includes a number of utility methods, among them
toUpperCase() , and
valueOf() . The latter method is indispensable in converting user input strings to numbers. The
Number subclasses also have methods for converting strings to numbers and vice versa.
In addition to the
String class, there is also a StringBuilder class. Working with
StringBuilder objects can sometimes be more efficient than working with strings. The
StringBuilder class offers a few methods that can be useful for strings, among them
reverse() . In general, however, the
String 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 the