The Char type is used to represent letters (both uppercase and lowercase), digits, and other symbols. Each character is just a symbol enclosed in single quotes.
val lowerCaseLetter = 'a'
val upperCaseLetter = 'Q'
val number = '1'
val space = ' '
val dollar = '$'This type can represent any symbol including hieroglyphs, as well as some special symbols.
A character can be also created using its hexadecimal code in the Unicode table. The code starts with
\u.val ch = '\u0040' // it represents '@'
println(ch) // @Although we use a sequence of characters to represent such code, the code itself represents exactly one character.
For example, Latin capital letters have hexadecimal codes from
'\u0041' to '\u005A', and Latin small letters have codes from '\u0061' to '\u007A'.Retrieving subsequent characters
There are two operators for adding (
+) and subtracting (-) integer numbers in order to get the next and previous character according to the Unicode order.val ch1 = 'b'
val ch2 = ch1 + 1 // 'c'
val ch3 = ch2 - 2 // 'a'It is possible to use increment (
++) and decrement (--) operators in prefix and postfix forms. The assignment operator combined with + or - also works, as well as +=, -= for characters.var ch = 'A'
ch += 10
println(ch) // 'K'
println(++ch) // 'L'
println(++ch) // 'M'
println(--ch) // 'L'Note: It is not possible to multiply and divide characters by numbers.
Escape sequences
There are some special characters starting with backslash
\, which are known as escape or control sequences. Most of them do not have corresponding symbols, and cannot be found on a keyboard. To represent such characters, we use a pair of regular symbols. In a program, this pair will be considered as exactly one character with the appropriate code. '\n'is the newline character;'\t'is the tab character;'\r'is the carriage return character;'\\'is the backslash character itself;'\''is the single quote mark;'\"'is the double quote mark.
Here are several examples:
print('\t') // makes a tab
print('a') // prints 'a'
print('\n') // goes to a new line
print('c') // prints 'c'This code prints:
a
cNote: There is also a character to represent a single space
' '. It is just a regular character, not an escape sequence.Relational operations with characters
Characters can be compared using relational operations (
=, <, >, <=, >=, !=) according to their position in the Unicode table.println('a' < 'c') // true
println('x' >= 'z') // false
println('D' == 'D') // true
println('Q' != 'q') // true, because capital and small letters are not the same
println('A' < 'a') // true, because capital Latin letters are placed before small onesUsing relational operations and codes we can check whether a char is a digit or not. All ten digits have codes from
'\u0030' to '\u0039'.Here is a program to do that:
import java.util.*
fun main(args: Array<String>) {
val scanner = Scanner(System.`in`)
val ch = scanner.next().first()
val isDigit = ch in '\u0030'..'\u0039'
println(isDigit)
}Note,
scanner doesn't have a function to read characters. Instead, we read a string and takes its first character.If the input is a digit
'0', '1', '2', ..., '9' (without quotes), the program prints true. Otherwise, it prints false.Processing characters
Each character has a set of useful functions. These functions can be used instead of working with codes.
isDigit()returnstrueif the given character represents a digit ('1','2', etc); otherwise,false;isLetter()returnstrueif the given character represents a letter ('a','B','m', etc); otherwise,false;isLetterOrDigit()returnstrueif the given character represents a letter or a digit; otherwise,false;isWhitespace()returnstrueif the given character represents a whitespace (' 'or'\t'or'\n'); otherwise,false;isUpperCase()returnstrueif the given character is an uppercase character; otherwise,false;isLowerCase()returnstrueif the given character is a lowercase character; otherwise,false;toUpperCase()returns the uppercase form of the given character;toLowerCase()returns the lowercase form of the given character.
Let's look at some examples of the listed functions:
val one = '1'
val isDigit = one.isDigit() // true
val isLetter = one.isLetter() // false
val capital = 'A'
val small = 'e'
val isLetterOrDigit = capital.isLetterOrDigit() // true
val isUpperCase = capital.isUpperCase() // true
val isLowerCase = capital.isLowerCase() // false
val capitalE = small.toUpperCase() // 'E'Naturally, there are a number of useful functions which we will learn throughout this course.