>> The Road
to Membership and Baeldung Pro
.
Going into ads,
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, and bit about how
Baeldung works if you're curious :)
2. Defining a
String
We can define a
String
as a single line
String
wrapped in double-quotes
:
val singleLineString = "Hello, I am a single line string"
Additionally,
it can be defined as a multi-line
String
wrapped in three double quotes
:
val multiLineString = """Hello, I am
|a multiline
|String""".stripMargin
With the
pipe
character and
stripMargin
method, we just left-justified our text.
3.
String
Equality
Comparing two
Strings
in Scala is handled using the
==
operator
. First, the method checks for potential null values, and then calls the
equals
method on
String
to compare:
4.
String
Concatenation
We can concatenate
String
s using the
concat
method or the
+
operator
:
val askTheTimeString = "...What time is it?"
val concatStrWithConcat = singleLineString.concat(askTheTimeString)
assert(concatStrWithConcat == "Hello, I am a single line string...What time is it?")
val concatStr = singleLineString + askTheTimeString
assert( concatStr == "Hello, I am a single line string...What time is it?")
5.
String
Matching with Regular Expressions
Scala supports regular expressions through the
Regex
class
, available in the
scala.util.matching
package. Using the
r
method on a
String
, we can convert it to a
Regex
instance, where we can perform
String
matching:
val testString = "this is a string with numbers 123456"
val regEx: Regex = "^(?=.*[a-zA-Z])(?=.*[0-9])".r
val result = regEx
.findFirstMatchIn(testString)
.isDefined
assertTrue(result == true)
In the above example, we’re checking if a
String
contains both letters and numbers.
It’s also possible to match groups of regular expressions
using parenthesis, so let’s see how it works and first define a multi-line
String
:
val testString = """property1: value1
|property2: value2
|property"""
Suppose we want to match all the key-value properties contained in the multi-line String. To achieve this, we can define a group of regular expressions and match them:
val regExGroup = "([0-9a-zA-Z- ]+): ([0-9a-zA-Z-#()/. ]+)".r
val matchResults = regExGroup.findAllMatchIn(testString)
As a result, the match will contain only the key-value properties that match the regular expressions:
val matchedStrings = matchResult
.map(regExMatch =>
s"key: ${(regExMatch.group(1)} value: ${(regExMatch.group(2)}"
).mkString(System.lineSeparator)
val expected = """key: property1 value: value1
|key: property2 value: value2"""
.stripMargin
assert(matchedStrings.equals(expected))
6. String Interpolation
String interpolation in Scala can be obtained with s, f, and raw methods.
Using s interpolation we can use our variables directly in the literal String, for instance:
val age = 30
val agePresentation = s"I am $age"
assert("I am 30" == agePresentation)
With f interpolation we have type-safe interpolation:
val >val name = "Michele"
val interpStr = f"My name is $name%s. I am $age%d years old and $height%1.2f meters tall"
assert(interpStr == "My name is Michele. I am 30 years old and 1,70 meters tall")
Finally, raw interpolation is similar to s interpolation except that it doesn’t escape literals:
val result = raw"My name is $name%s. \n $agePresentation and $height%1.2f meters tall"
assert(result == "My name is Michele%s. \\n I am 30 and 1.7%1.2f meters tall")
7. Conclusion
In this article, we looked at some of the main operations that we can do with Strings in Scala. As usual, the full source code can be found over on GitHub.
