The addAll(Collection C) method of Java AbstractCollection is used to append all of the elements from a mentioned collection to this collection. The elements are added randomnly without following any specific order.
boolean addAll(Collection C)
Parameters: The parameter C is a collection of any type that is to be added to the collection.
Return Value: The method returns true if it successfully appends the elements of the collection C to the existing collection otherwise it returns False.
Below programs illustrate the AbstractCollection.addAll() method:
AbstractCollection 1: [4, Geeks, To, TreeSet, Welcome] AbstractCollection 2:  AbstractCollection 2: [4, Geeks, To, TreeSet, Welcome]
AbstractCollection 1: [10, 20, 30, 40, 50] AbstractCollection 2:  AbstractCollection 2: [10, 20, 30, 40, 50]
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