How to Work With Collections In Groovy?

9 minutes read

In Groovy, working with collections is made easy with the built-in methods and enhancements provided by the language. You can perform common operations on collections such as filtering, mapping, reducing, iterating, and grouping elements without the need for complex syntax.


Groovy provides a variety of methods like collect, findAll, inject, findAll, each, any, find, and groupBy to manipulate collections in a concise and readable way. You can also use closures and lambda expressions to define custom behavior for these operations.


Additionally, Groovy supports both mutable and immutable collections like lists, sets, and maps. You can easily convert between different types of collections using the toList, toSet, and toMap methods.


Overall, working with collections in Groovy is intuitive and efficient due to the language's powerful features and syntax sugar. You can quickly write clean and concise code to handle collection data in a functional and expressive manner.

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What is the syntax for creating a Set in Groovy?

To create a Set in Groovy, you can use the following syntax:

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def mySet = new HashSet()


Alternatively, you can also create a Set using the shorthand syntax:

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def mySet = []


Both of these syntax options will create an empty Set in Groovy.


What is the syntax for creating a Range in Groovy?

The syntax for creating a Range in Groovy is as follows:

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def range = 1..10 // Creates a range from 1 to 10 (inclusive)

// You can also create a Range with a step value
def rangeWithStep = 1..10 step 2 // Creates a range from 1 to 10 with a step of 2

// You can use square brackets to exclude the upper bound
def rangeExclusive = 1..<10 // Creates a range from 1 to 9



How to convert elements in a collection to lowercase in Groovy?

You can convert elements in a collection to lowercase in Groovy using the collect method. Here's an example:

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def collection = ["Hello", "WORLD", "gRoOvY"]

def lowerCaseCollection = collection.collect { it.toLowerCase() }

println lowerCaseCollection


This code snippet will output:

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[hello, world, groovy]


In this example, the collect method is used to iterate over each element in the collection and apply the toLowerCase() method to convert it to lowercase. The result is stored in the lowerCaseCollection variable.


How to remove duplicate elements from a collection in Groovy?

One way to remove duplicate elements from a collection in Groovy is by converting the collection to a Set which automatically removes duplicates. Here's an example:

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def list = [1, 2, 2, 3, 4, 4, 5]
def uniqueList = list as Set
println uniqueList


This will output:

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[1, 2, 3, 4, 5]


Another way is to use the unique() method which returns a new list with duplicate elements removed:

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def list = [1, 2, 2, 3, 4, 4, 5]
def uniqueList = list.unique()
println uniqueList


This will also output:

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[1, 2, 3, 4, 5]


Both of these methods will give you a collection without any duplicate elements.


What is the purpose of the inject method in Groovy?

The inject method in Groovy is used to iterate over a collection and accumulate a result by applying an operation to each element of the collection. It is similar to the reduce method in other programming languages. The inject method takes an initial value and a closure as arguments, and for each element in the collection, the closure is applied with the current accumulated value and the element as parameters to compute a new accumulated value. The result is returned once all elements of the collection have been processed. This method is commonly used for summing up values, concatenating strings, or performing other operations that require accumulating a result.


What is the default capacity of a List in Groovy?

The default initial capacity of a List in Groovy is 10. However, the list automatically grows in size as new elements are added to it.

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