Scala Strings

The following example assigns a string value 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 as a string constant, its type is String (java.lang.String).

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

In Scala, String is an immutable object, so the 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 in the next section.

String Creation

String Creation Examples:

var　greeting　=　"Hello　World!";
or
var　greeting:String　=　"Hello　World!";

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

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

Example

object　Test　{
　　　val　greeting:　String　=　"Hello,　World!"
　　　def　main(args:　Array[String])　{
　　　　　　println(　greeting　)
　　　}
}

Execute the above code, and the output result is:

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

As mentioned earlier, String objects are immutable. If you need to create a modifiable string, you can use the StringBuilder class, as shown 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　);
　　　}
}

Execute the above code, and the output result is:

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

String Length

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

Online Example

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

Execute the above code, and the output result is:

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

String Concatenation

The concat() method is used in the String class to concatenate two strings:

string1.concat(string2);

Example Demonstration:

scala>　"Basic Tutorial Website Official:　".concat("www.oldtoolbag.com");
res0:　String　=　Basic Tutorial Website Official:　www.oldtoolbag.com

Similarly, you can also use the plus sign (+) to connect:

scala>　"Basic Tutorial Website Official:　"　+　"　www.oldtoolbag.com"
res1:　String　=　Basic Tutorial Website official website:　　www.oldtoolbag.com

Let's look at a complete example:

Example

object　Test　{
　　　def　main(args:　Array[String])　{
　　　　　　var　str1　="Basic Tutorial Website official website: ";
　　　　　　var　str2　=　　"www.oldtoolbag.com";
　　　　　　var　str3　=　　"The Slogan of Basic Tutorial Website is: ";
　　　　　　var　str4　=　　"Learn the basics, and you can go further!";
　　　　　　println(　str1　+　str2　);
　　　　　　println(　str3.concat(str4);
　　　}
}

Execute the above code, and the output result is:

$ scalac  Test.scala
$ scala  Test
Basic Tutorial Website official website: www.oldtoolbag.com
The Slogan of Basic Tutorial Website is: Learn the basics, and you can go further!

Create a formatted string

In the String class, you can use the printf() method to format strings and output them. The String format() method returns a String object rather than 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　=　"Basic Tutorial Website!"
　　　　　　var　fs　=　printf("floating-point variable is　"　+
　　　　　　　　　　　　　　　　　　　"%f,　integer variable is　%d,　string is　"　+
　　　　　　　　　　　　　　　　　　　"　%s",　floatVar,　intVar,　stringVar)
　　　　　　println(fs)
　　　}
}

Execute the above code, and the output result is:

$ scalac  Test.scala
$ scala  Test
The floating-point variable is　12.456000, the integer variable is　2000, the string is 　Basic Tutorial Website!()

String Methods

The following table lists the commonly used methods in java.lang.String, which you can use in Scala:

Serial Number	Method and Description
1	char charAt(int index) Return the character at the specified position
2	int compareTo(Object o) Compare a string with an object
3	int compareTo(String anotherString) Compare two strings in dictionary order
4	int compareToIgnoreCase(String str) Compare two strings in dictionary order, ignoring case
5	String concat(String str) Concatenate the specified string to the end of this string
6	boolean contentEquals(StringBuffer sb) Compares this string with the specified StringBuffer
7	static String copyValueOf(char[] data) Returns a new string that represents the specified character sequence
8	static String copyValueOf(char[] data, int offset, int count) Returns a new string that represents the specified character sequence
9	boolean endsWith(String suffix) Tests if this string ends with the specified suffix
10	boolean equals(Object anObject) Compares this string to the specified object
11	boolean equalsIgnoreCase(String anotherString) Compares this string to another string, ignoring case
12	byte getBytes() Encodes this string into a sequence of bytes using the platform's default character set, and stores the result into a new byte array
13	byte[] getBytes(String charsetName Encodes this string into a sequence of bytes using the specified character set, and stores the result into a new byte array
14	void getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin) Copies characters from this string into the destination character array
15	int hashCode() Returns the hash code value for the string
16	int indexOf(int ch) Returns the index within this string of the first occurrence of the specified character
17	int indexOf(int ch, int fromIndex) Returns the index within this string of the first occurrence of the specified character, starting at the specified index
18	int indexOf(String str) Returns the index within this string of the first occurrence of the specified substring
19	int indexOf(String str, int fromIndex) Returns the index within this string of the first occurrence of the specified substring, starting at the specified index
20	String intern() Returns the normalized representation of the string object
21	int lastIndexOf(int ch) Returns the index of the last occurrence of the specified character in this string.
22	int lastIndexOf(int ch, int fromIndex) Return the index of the last occurrence of the specified character in this string, starting from the specified index and searching backward
23	int lastIndexOf(String str) Return the index of the rightmost occurrence of the specified substring in this string
24	int lastIndexOf(String str, int fromIndex) Return the index of the last occurrence of the specified substring in this string, starting from the specified index and searching backward
25	int length() Return the length of this string
26	boolean matches(String regex) Inform whether this string matches the given regular expression
27	boolean regionMatches(boolean ignoreCase, int toffset, String other, int ooffset, int len) Test whether two string regions are equal
28	boolean regionMatches(int toffset, String other, int ooffset, int len) Test whether two string regions are equal
29	String replace(char oldChar, char newChar) Return a new string that is obtained by replacing all occurrences of oldChar in this string with newChar
30	String replaceAll(String regex, String replacement Replace all occurrences of substrings of this string that match the given regular expression with the given replacement
31	String replaceFirst(String regex, String replacement) Replace the first substring of this string that matches the given regular expression with the given replacement
32	String[] split(String regex) Split this string based on the matches of the given regular expression
33	String[] split(String regex, int limit) Split this string based on the given regular expression
34	boolean startsWith(String prefix) Test whether this string starts with the specified prefix
35	boolean startsWith(String prefix, int toffset) Test whether the substring of this string starting from 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 white space from the specified string
46	static String valueOf(primitive data type x) Returns the string representation of the specified type parameter

Scala Arrays Scala Closures

Scala Tutorial

Scala Strings

String Creation

String Length

Online Example

String Concatenation

Create a formatted string

String Methods