How to Do Pattern Match In Groovy Script?

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Pattern matching in Groovy script can be done using regular expressions. Regular expressions are sequences of characters that define a search pattern, allowing you to match and manipulate strings based on specific patterns.


To perform pattern matching in Groovy, you can use the =~ operator along with regular expression patterns. Here is an example that demonstrates pattern matching in a Groovy script:

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def text = "Hello, World!"

// Pattern matching using the =~ operator
if (text =~ /Hello/) {
    println("Pattern matched!")
} else {
    println("Pattern not found!")
}


In the above example, the /Hello/ is a regular expression pattern. The =~ operator is used to perform pattern matching on the text variable. If the pattern is found within the text, the "Pattern matched!" message will be printed; otherwise, "Pattern not found!" will be printed.


You can use various regular expression syntax and features to create more complex patterns for matching strings. Regular expression patterns can include metacharacters, quantifiers, character classes, and more, allowing you to define precise patterns to match text in a flexible manner.


Pattern matching in Groovy is widely used for tasks such as extracting specific information from strings, validating input, replacing parts of a string, and many other text manipulation tasks.

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What is the significance of using character classes in pattern matching with Groovy?

Character classes in pattern matching with Groovy allow you to search for specific patterns of characters within a string. They are enclosed in square brackets [] and define a set of characters that can match at a specific position in the string.


The significance of using character classes in pattern matching with Groovy is that they provide a powerful and flexible way to match a single character against a set of possible characters. Instead of specifying individual characters, you can define a range of characters or a predefined set of characters using predefined character classes like \d (matches any digit), \w (matches any word character), and \s (matches any whitespace character).


Using character classes can simplify your patterns and make your code more concise. It allows you to write more generic expressions that can match multiple possibilities. It also provides an easy way to search for characters that fall within a specific range or belong to a predefined set, without specifying each character individually.


For example, the pattern [a-z] matches any lowercase letter, [A-Z] matches any uppercase letter, [0-9] matches any digit, and [\d\s] matches any digit or whitespace character.


Overall, character classes in pattern matching with Groovy offer a convenient way to specify sets of characters that can be matched against in order to find specific patterns within a string.


How to match a single character in a specific position using Groovy pattern matching?

To match a single character in a specific position using Groovy pattern matching, you can use the ^ and $ anchors along with the appropriate regular expression pattern.


Here is an example code snippet demonstrating how to achieve this:

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def input = 'Hello World'

// Match if the second character is 'e'
if (input =~ /^.(e).$/) {
    println "Match found! The second character is 'e'"
} else {
    println "No match found"
}


In this example, the ^ anchor matches the start of the string, . matches any single character, (e) captures the second character which must be 'e', and the $ anchor matches the end of the string. By enclosing (e) in parentheses, we can capture the matched character and use it for further processing if needed.


What are some commonly used anchors in pattern matching with Groovy?

Some commonly used anchors in pattern matching with Groovy are:

  1. ^ (caret): It matches the start of a line. For example, the pattern ^Hello matches a line that starts with "Hello".
  2. $ (dollar sign): It matches the end of a line. For example, the pattern world$ matches a line that ends with "world".
  3. \b (word boundary): It matches a word boundary, i.e., the position between a word character and a non-word character. For example, the pattern \btest\b matches the word "test" but not "testing" or "contest".
  4. \B (non-word boundary): It matches a position that is not a word boundary. For example, the pattern \Btest\B matches the word "test" only if it appears within another word.
  5. (?i) (case-insensitive flag): It makes the pattern case-insensitive. For example, the pattern (?i)hello matches "hello", "Hello", "HELLO", etc.
  6. (?m) (multiline flag): It enables multiline mode, where ^ and $ match the start and end of each line instead of the whole input string.
  7. (?s) (dotall flag): It enables the dot (.) to match all characters including newline characters. By default, the dot matches any character except a newline.


How to extract multiple patterns from a string in Groovy?

In Groovy, you can use regular expressions and the findAll method to extract multiple patterns from a string. Here's an example:

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def inputString = "This is a sample string 12345 with multiple patterns to extract."

def pattern1 = /\d+/  // Match one or more digits
def pattern2 = /[A-Z]+/  // Match one or more uppercase letters
def pattern3 = /[a-z]+/  // Match one or more lowercase letters

def matches1 = inputString.findAll(pattern1)
def matches2 = inputString.findAll(pattern2)
def matches3 = inputString.findAll(pattern3)

println matches1
println matches2
println matches3


In this example, the findAll method is used to find all occurrences of each pattern in the inputString. The matches are then stored in separate variables (matches1, matches2, matches3) which you can use as per your requirement.


What is the role of the 'group' method in pattern matching with Groovy?

The 'group' method in pattern matching with Groovy is used to retrieve the matched portions of a string that correspond to capturing groups in a regular expression.


When a regular expression pattern contains capturing groups (defined by parentheses), the 'group' method allows you to access and retrieve the matched substrings of these groups. The 'group' method is available on the Matcher object that is returned by the 'find' or 'match' methods of the java.util.regex.Pattern class in Groovy.


Here is an example to illustrate its usage:

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def text = "Hello World!"
def pattern = /(\w+)\s(\w+)/

def matcher = pattern.matcher(text)
if (matcher.find()) {
    println "Full match: ${matcher.group(0)}"
    println "First group: ${matcher.group(1)}"
    println "Second group: ${matcher.group(2)}"
}


In the above code, the pattern captures two word groups using the regular expression (\w+)\s(\w+). The 'group' method is then used to retrieve and print the matched substrings: the full match, the first captured group, and the second captured group.


Output:

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Full match: Hello World
First group: Hello
Second group: World


Therefore, the 'group' method plays a key role in pattern matching with Groovy by allowing you to extract and utilize the specific matched portions of a string that correspond to capturing groups defined in a regular expression.

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