Scala Strings - Scala

What is Scala - Strings?

This chapter explains you about the Scala Strings. In Scala, as in Java, a string is an immutable object, that is, an object that cannot be modified. On the other hand, the objects that can be modified, like arrays, are called mutable objects. Strings are also very useful objects, in the rest of this section, we present some important methods of 'java.lang.String' class.

Creating a String

The following code can be used to create a String -

Whenever the compiler encounters a string literal in the code, it immediately creates a String object with its value, in the above case, “Hello world!”. String keywords can also be given in alternate declaration as shown above.

Try the following example program.

Example

Save the above program in Demo.scala. The following commands can be used to compile and execute this program.

Command

Output

As mentioned earlier, String class is immutable. String objects once created cannot be changed. If there is any necessity to make a lot of modifications to the Strings of characters then we use String Builder Class available in Scala!.

String Length

Methods which are used to obtain information about an object are known as accessor methods. One accessor method which can be used with strings is the length() method, which returns the number of characters contained in the string object.

Use the following code segment to find the length of a string -

Example

Save the above program in Demo.scala. The following commands can be used to compile and execute this program.

Command

Output

Concatenating Strings

The String class includes a method for concatenating two strings -

This returns a new string that is string1 with string2 added to it at the end. You can also use the concat() method with string literals, as in -

Strings are more commonly concatenated with the + operator, as in -

Which results in -

The following lines of code to find string length.

Example

Save the above program in Demo.scala. The following commands can be used to compile and execute this program.

Command

Output

Creating Format Strings

You have both printf() and format() methods to print output with the formatted numbers. The String class has an equivalent class method, format(), that returns a String object rather than a PrintStream object.

Try the below example program, which makes use of printf() method -

Example

Save the above program in Demo.scala. The following commands are used to compile and execute this program.

Command

Output

String Interpolation

String Interpolation is a new way to create Strings in the Scala programming language. This feature supports the versions of all Scala-2.10 and later. String Interpolation: The mechanism to embed variable references directly in process string literal.

There are three types (interpolators) of implementations in String Interpolation.

The ‘s’ String Interpolator

The literal ‘s’ allows the usage of the variable directly in processing a string, when you prepend ‘s’ to it. Any String variable with in a scope and that can be used with in a String. The following are the different usages of ‘s’ String interpolator.

The following example code snippet for the implementation of ‘s’ interpolator in appending String variable ($name) to a normal String (Hello) in println statement.

String interpolater can also process arbitrary expressions. The following code snippet for Processing a String (1 + 1) with arbitrary expression (${1 + 1}) using ‘s’ String interpolator. Any arbitrary expression can be embedded in ‘${}’.

Try the below example program of implementing ‘s’ interpolator.

Example

Save the above program in Demo.scala. The following commands can be used to compile and execute this program.

Command

Output

The ‘ f ’ Interpolator

The literal ‘f’ interpolator allows us to create a formatted String, similar to the printf in C language. While using the ‘f’ interpolator, all variable references should be followed by the 'printf' style format specifiers such as %d, %i, %f, etc.

Let us consider an example of append floating point value (height = 1.9d) and String variable (name = “James”) with normal string. The following code snippet of implementing ‘f’ Interpolator. Here $name%s to print (String variable) James and $height%2.2f to print (floating point value) 1.90.

It is type safe (i.e.) the variable reference and following the format specifier should match otherwise it is shows an error. The ‘ f ’ interpolator makes use of the String format utilities (format specifiers) available in Java. By default means, there is no % of character after the variable reference. It will assume as %s (String).

‘raw’ Interpolator

The ‘raw’ interpolator is very similar to the ‘s’ interpolator except that it performs no escaping of literals within a string. The following code snippets in the below table will differ the usage of ‘s’ and ‘raw’ interpolators. In outputs of ‘s’ usage ‘\n’ effects as new line and in the output of ‘raw’ usage and the ‘\n’ will not effect. String MethodsIt will print the complete string with escape letters.

‘s’ interpolator usage

‘raw’ interpolator usage

Program

Program

Output

Output

Following is the list of methods defined by the 'java.lang.String'class and can be used directly in your Scala programs -

Sr.No
Methods with Description
1
char charAt(int index)
Returns the character at the specified index.
2
int compareTo(Object o)
Compares this String to another Object.
3
int compareTo(String anotherString)
Compares two strings lexicographically.
4
int compareToIgnoreCase(String str)
Compares two strings lexicographically, ignoring case differences.
5
String concat(String str)
Concatenates the specified string to the end of this string.
6
boolean contentEquals(StringBuffer sb)
Returns true if and only if this String represents the same sequence of characters as the specified StringBuffer.
7
static String copyValueOf(char[] data)
Returns a String that represents the character sequence in the array specified.
8
static String copyValueOf(char[] data, int offset, int count)
Returns a String that represents the character sequence in the array specified.
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 considerations.
12
byte getBytes()
Encodes this String into a sequence of bytes using the platform's default charset, storing the result into a new byte array.
13
byte[] getBytes(String charsetName)
Encodes this String into a sequence of bytes using the named charset, storing 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 a hash code for this 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 the search 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
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.
21
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.
22
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.
23
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.
24
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.
25
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.
26
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.
27
boolean regionMatches(boolean ignoreCase, int toffset, String other, int offset, int len)

Tests if two string regions are equal.
28
boolean regionMatches(boolean ignoreCase, int toffset, String other, int offset, int len)

Tests if two string regions are equal.
29
boolean regionMatches(boolean ignoreCase, int toffset, String other, int offset, int len)

Tests if two string regions are equal.
30
String replaceAll(String regex, String replacement

Replaces each substring of this string that matches the given regular expression with the given replacement.
31
String replaceFirst(String regex, String replacement)

Replaces the first substring of this string that matches the given regular expression with the given replacement.
32
String[] split(String regex)

Splits this string around matches of the given regular expression.
33
String[] split(String regex, int limit)

Splits this string around 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 this string starts with the specified prefix beginning a specified index.
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 of the characters in this String to lower case using the rules of the default locale.
41
String toLowerCase(Locale locale)

Converts all of the characters in this String to lower case using the rules of the given Locale.
42
String toString()

This object (which is already a string!) is itself returned.
43
String toUpperCase()

Converts all of the characters in this String to upper case using the rules of the default locale.
44
String toUpperCase(Locale locale)

Converts all of the characters in this String to upper case using the rules of the given Locale.
45
String trim()

Returns a copy of the string, with leading and trailing whitespace omitted.
46
static String valueOf(primitive data type x)

Returns the string representation of the passed data type argument.

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