String Literals
String Literals are a way to express text for use in programs. There are two types of String Literals, single-quoted and double-quoted ones, both of which have their own special semantics.
Single-Quoted String Literals are indicated and terminated with a single quote
'.'hello world'
'a'
'"Single-qouted strings can contain double-quotes", he said'
The type of Single-Quoted String Literals is inferred as
java.lang.String. However, it is possible to use them as char literals by explicitly stating that this type is wanted:'a' as char
let c: char = 'C'
This is only possible if the Single-Quoted String consists of exactly one character (Unicode code-point).
Double-Quoted String Literals being and end with a double-quote symbol
". This means they cannot contain this character, for example for quotes within the text."Hello World"
"a"
"'Double-quoted Strings can contain single-quotes', she said"
""this is not possible" - the compiler" // error
The type of Double-Quoted String Literals is always inferred as
java.lang.String. Explicitly or implicitly casting to char causes a semantic error.Both types of String Literals can span multiple lines by simply adding a newline in the body of the literal.
"This is a multi-line
string"
To avoid problems with indentation, tab characters are ignored in String Literals:
class Test
{
String s = "Hello,
World"
}
It is possible to insert certain special characters into String Literals via Escape Sequences. They are indicated by a backslash
\ followed by a single symbol. The symbol determines the character that is actually inserted into the String.let tab: char = '\t'
let cr: char = '\r'
The following table shows the escape sequences and the symbols that are actually inserted:
Escape Symbol | Actual Symbol | Unicode Number |
\n | New Line | U+000A |
\t | Horizontal Tab | U+0009 |
\r | Carriage Return | U+000D |
\f | Form Feed | U+000C |
\b | Backspace | U+0008 |
To be able to use
' and " in single-quoted or double-quoted String Literals respectively, they can be escaped as well. This will ensure that they are treated as part of the literal, not as the terminating symbol.println "\"this is possible\" - the compiler"
println '> \' and this as well\' <'
The above code will print
"this is possible" - the compiler
> 'and this as well' <
To insert a backslash symbol, you can use
\\.String path = '..\\path\\to\\file\\'
The value of the
path variable will now be..\path\to\file
By escaping an opening parenthesis symbol
\(, one can make use of String Interpolation in Double-Quoted String Literals. The next closing parenthesis will then be treated as the continuation of the String.let value: int = 10
let s: String = "The value is: \(value)."
print s // prints 'The value is: 10.'
Note that this feature is only supported in Double-Quoted String Literals.
Verbatim Strings are a way to create Strings with many characters that would otherwise need to be escaped. This is especially handy for file paths in certain operating systems:
let path: String = @"..\path\to\file"
Or for use as RegExp's, where you sometimes want to match characters literally:
let regex: String = @"Hello\.World" // "\." means "a literal dot symbol" in RegExp
let pattern = Pattern.compile(regex)
pattern.matches("Hello.World") // => true
pattern.matches("Hello|World") // => false
In the example, the pattern expects a literal dot
. rather than any character.Last modified 4yr ago