Groovy: List: remove element from the list

Groovy provides number of ways to remove an element from the list.

a.   Using removeAt method

b.   Using removeElement method

c.    Using removeAll method

d.   Using minus method

e.   Using – operator

f.     Using pop method

Using removeAt method

public Object removeAt(int index)

This method removes the element from the list and return the removed element.

HelloWorld.groovy

primes = [2, 3, 5, 7, 11, 13, 17, 19]

println primes

removedElement = primes.removeAt(4)

println "Removed Element : $removedElement"
println primes

Output

[2, 3, 5, 7, 11, 13, 17, 19]

Removed Element : 11

[2, 3, 5, 7, 13, 17, 19]

Using removeElement method

public boolean removeElement(Object o)

This method removes the element from list. It returns true, if the element removed from list, else false.

HelloWorld.groovy

primes = [2, 3, 5, 7, 11, 13, 17, 19]

println primes

boolean isRemoved = primes.removeElement(17)

if(isRemoved){
 println "17 is removed from list"
}else{
 println "17 is not found from list"
}

println primes

Output

[2, 3, 5, 7, 11, 13, 17, 19]

17 is removed from list

[2, 3, 5, 7, 11, 13, 19]

Using removeAll method

public boolean removeAll(Closure condition)

Remove the elements from list that satisfies given condition.

public boolean removeAll(Object[] items)

Remove all the items from given list.

HelloWorld.groovy

numbers = [0, 1, 2, 3, 4, 5, 3, 2, 1, 10]
println "$numbers"

println "\nRemoving all the elements that are < 3"
numbers.removeAll{it < 3}
println "$numbers"

println "\nRemoving the elements [3, 10]"
numbers.removeAll([3, 10])
println "$numbers"

Output

[0, 1, 2, 3, 4, 5, 3, 2, 1, 10]

Removing all the elements that are < 3

[3, 4, 5, 3, 10]

Removing the elements [3, 10]

[4, 5]

Using minus method

public Collection minus(Iterable removeMe)

Creates new collection by removing given elements from this list

public Collection minus(Object removeMe)

Creates new collection by removing given element.

HelloWorld.groovy

numbers = [0, 1, 2, 3, 4, 5, 3, 2, 1, 10]
println "numbers: $numbers"

println "Getting new list by removing [0, 2, 4, 6, 8, 10]"
oddNumbers = numbers.minus([0, 2, 4, 6, 8, 10])
println "\nnumbers: $numbers"
println "oddNumbers: $oddNumbers"

println "Removing 0 from numbers"
exceptZero = numbers.minus(0)
println "\nnumbers: $numbers"
println "exceptZero: $exceptZero"

Output

numbers: [0, 1, 2, 3, 4, 5, 3, 2, 1, 10]

Getting new list by removing [0, 2, 4, 6, 8, 10]

numbers: [0, 1, 2, 3, 4, 5, 3, 2, 1, 10]

oddNumbers: [1, 3, 5, 3, 1]

Removing 0 from numbers

numbers: [0, 1, 2, 3, 4, 5, 3, 2, 1, 10]

exceptZero: [1, 2, 3, 4, 5, 3, 2, 1, 10]

Using minus operator

It implicitly calls minus method.

HelloWorld.groovy

numbers = [0, 1, 2, 3, 4, 5, 3, 2, 1, 10]
println "numbers: $numbers"

println "Getting new list by removing [0, 2, 4, 6, 8, 10]"
oddNumbers = numbers - ([0, 2, 4, 6, 8, 10])
println "\nnumbers: $numbers"
println "oddNumbers: $oddNumbers"

println "Removing 0 from numbers"
exceptZero = numbers - 0
println "\nnumbers: $numbers"
println "exceptZero: $exceptZero"

Output

numbers: [0, 1, 2, 3, 4, 5, 3, 2, 1, 10]

Getting new list by removing [0, 2, 4, 6, 8, 10]

numbers: [0, 1, 2, 3, 4, 5, 3, 2, 1, 10]

oddNumbers: [1, 3, 5, 3, 1]

Removing 0 from numbers

numbers: [0, 1, 2, 3, 4, 5, 3, 2, 1, 10]

exceptZero: [1, 2, 3, 4, 5, 3, 2, 1, 10]

Using pop method

public Object pop()

pop() method removes the first element from list.

HelloWorld.groovy

numbers = [0, 1, 2, 3, 4, 5, 3, 2, 1, 10]
int length = numbers.size()

println "numbers : $numbers"
for(int i = 0; i < length; i++){
 removed = numbers.pop()
 println "removed : $removed"
 println "numbers : $numbers"
}

Output

numbers : [0, 1, 2, 3, 4, 5, 3, 2, 1, 10]

removed : 0

numbers : [1, 2, 3, 4, 5, 3, 2, 1, 10]

removed : 1

numbers : [2, 3, 4, 5, 3, 2, 1, 10]

removed : 2

numbers : [3, 4, 5, 3, 2, 1, 10]

removed : 3

numbers : [4, 5, 3, 2, 1, 10]

removed : 4

numbers : [5, 3, 2, 1, 10]

removed : 5

numbers : [3, 2, 1, 10]

removed : 3

numbers : [2, 1, 10]

removed : 2

numbers : [1, 10]

removed : 1

numbers : [10]

removed : 10

numbers : []

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