Scala Strings

The following example assigns a string to a constant:

Example

object Test {
    val greeting: String = "Hello,World!"

    def main(args: Array[String]) {
        println(greeting)
    }
}

The above example defines the variable greeting, a string constant, with its type as String (java.lang.String).

In Scala, the type of a string is actually Java String, and there is no String class in Scala itself.

In Scala, a String is an immutable object, so this object cannot be modified. This means that if you modify a string, a new string object will be created.

However, other objects, such as arrays, are mutable objects. We will introduce commonly used java.lang.String methods next.

Creating Strings

Create string instances as follows:

var greeting = "Hello World!";

or

var greeting: String = "Hello World!";

You do not necessarily have to specify the String type for a string, as the Scala compiler will automatically infer the type of the string as String.

Of course, we can also explicitly declare the string as a String type, as in the following example:

Example

object Test {
    val greeting: String = "Hello, World!"

    def main(args: Array[String]) {
        println(greeting)
    }
}

Executing the above code will produce the output:

$ scalac Test.scala
$ scala Test
Hello, world!

As we mentioned earlier, String objects are immutable. If you need to create a modifiable string, you can use the StringBuilder class, as in the following example:

Example

object Test {
    def main(args: Array[String]) {
        val buf = new StringBuilder;
        buf += 'a'
        buf ++= "bcdef"
        println("buf is : " + buf.toString)
    }
}

Executing the above code will produce the output:

$ scalac Test.scala
$ scala Test
buf is : abcdef

String Length

We can use the length() method to get the length of a string:

Example

object Test {
    def main(args: Array[String]) {
        var palindrome = "www.tutorialpro.org"
        var len = palindrome.length()
        println("String Length is : " + len)
    }
}

Executing the above code will produce the output:

$ scalac Test.scala
$ scala Test
String Length is : 14

String Concatenation

In the String class, the concat() method is used to concatenate two strings:

string1.concat(string2);

Example demonstration:

scala> "tutorialpro.org官网： ".concat("www.tutorialpro.org")
res0: String = tutorialpro.org官网： www.tutorialpro.org

You can also use the plus sign (+) to concatenate:

scala> "tutorialpro.org官网： " + " www.tutorialpro.org"
res1: String = tutorialpro.org官网：  www.tutorialpro.org

Let's look at a complete example:

Example

object Test {
    def main(args: Array[String]) {
        var str1 = "tutorialpro.org官网："
        var str2 = "www.tutorialpro.org"
        var str3 = "tutorialpro.org的 Slogan 为："
        var str4 = "学的不仅是技术，更是梦想！"
        println(str1 + str2)
        println(str3.concat(str4))
    }
}

Executing the above code will produce the output:

$ scalac Test.scala
$ scala Test
tutorialpro.org官网：www.tutorialpro.org
tutorialpro.org的 Slogan 为：学的不仅是技术，更是梦想！

Creating Formatted Strings

In the String class, you can use the printf() method to format strings and output, and the String format() method can return a String object instead of a PrintStream object. The following example demonstrates the use of the printf() method:

Example

object Test {
    def main(args: Array[String]) {
        var floatVar = 12.456
        var intVar = 2000
        var stringVar = "tutorialpro.org!"
        var fs = printf("浮点型变量为 " +
                       "%f, 整型变量为 %d, 字符串为 " +
                       " %s", floatVar, intVar, stringVar)
        println(fs)
    }
}

Executing the above code will produce the output:

``` $ scalac Test.scala $ scala Test 浮点型变量为 12.456000, 整型变量为 2000, 字符串为 | 33 | String[] split(String regex, int limit) Splits this string by the matches of the given regular expression | 34 | boolean startsWith(String prefix) Tests if this string starts with the specified prefix | 35 | boolean startsWith(String prefix, int toffset) Tests if the substring of this string beginning at the specified index starts with the specified prefix | 36 | CharSequence subSequence(int beginIndex, int endIndex) Returns a new character sequence that is a subsequence of this sequence | 37 | String substring(int beginIndex) Returns a new string that is a substring of this string | 38 | String substring(int beginIndex, int endIndex) Returns a new string that is a substring of this string | 39 | char[] toCharArray() Converts this string to a new character array | 40 | String toLowerCase() Converts all characters in this String to lowercase using the rules of the default locale | 41 | String toLowerCase(Locale locale) Converts all characters in this String to lowercase using the rules of the given Locale | 42 | String toString() Returns this object itself (it is already a string!) | 43 | String toUpperCase() Converts all characters in this String to uppercase using the rules of the default locale | 44 | String toUpperCase(Locale locale) Converts all characters in this String to uppercase using the rules of the given Locale | 45 | String trim() Removes leading and trailing whitespace from the specified string | 46 | static String valueOf(primitive data type x) Returns the string representation of the specified primitive data type argument