CODEWITHSUNDEEP
javacollections
Andy
Andy

Reputation: 9048

Why does java.util.Collection.remove() return a boolean?

Are there any real world examples of when a caller might use the value returned from Collection.remove()?

I'm happy that the method returns a boolean but am struggling to think of a case when the result would be useful to a caller.

Upvotes: 3

Views: 2231

Answers (2)

René Link
René Link

Reputation: 51383

As the javadoc says

Removes a single instance of the specified element from this collection, if it is present (optional operation).

The collection might contain multiple objects that are all equal, because a collection is not necessarily a Set.

So one use case might be to remove all instances of an object equal to the remove argument.

while(col.remove(anObject));

Remember that the javadoc also says:

More formally, removes an element e such that (o==null ? e==null : o.equals(e))

So if you get a collection that might contain null values and you only want to process the "real" objects, you can make this code easier

for(Object obj : col) {
    if(obj != null){
        doSomethingWithObject(obj);
    }
}

by removing the null values first:

while(col.remove(null));

for(Object obj : col) {
    doSomethingWithObject(obj); 
}

Upvotes: 4

Bohemian
Bohemian

Reputation: 425073

Collection.remove() returns false when the object passed to it was not found in the collection.

That sounds fairly useful to me, especially if you expected the object to be there - once removed it would be impossible to confirm that it previously was. The call to remove() is the last chance to discover it wasn't there.

Upvotes: 6

Related Questions