CODEWITHSUNDEEP
javacollections
bsiamionau
bsiamionau

Reputation: 8229

Advantages of removing element from collection as set with one object

I found next code in official java docs:

collection.removeAll(Collections.singleton(element));

I couldn't figure out advantages of this approach. Why not usual element removing?

collection.remove(element);

Thanks!

Upvotes: 4

Views: 169

Answers (4)

TheWhiteRabbit
TheWhiteRabbit

Reputation: 15758

When testing(unit testing). Collections.singleton is a one line way to turn your subject into a collection. The alternative is two lines and not onerous.

Upvotes: 0

pushy
pushy

Reputation: 9635

From the API

remove(Object o)
Removes a single instance of the specified element from this collection, if it is present

and:

removeAll(Collection c)
Removes all of this collection's elements that are also contained in the specified collection

So, if your collection has more than one occurance of the element you wish to remove, you would have to execute collection.remove(element) several times, but removeAll only once. As removeAll takes a collection as argument, Collection.singleton can offer you a convenient way to create a collection with only one argument.

Upvotes: 3

Azodious
Azodious

Reputation: 13872

Acc. to docs:

consider the following idiom to remove all instances of a specified element, e, from a Collection, c

collection.removeAll(Collections.singleton(element));

while collection.remove(element); removes a single instance of the specified element from this collection

So, to remove all instances, you've to use a loop construct with latter approach. while with first one it's just one line job.

Upvotes: 5

Mikhail Vladimirov
Mikhail Vladimirov

Reputation: 13890

The former removes all occurrences of the element within collection, the latter removes only first occurrence.

Upvotes: 8

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