Explain Java 8-Internal vs. External Iteration?

External Iterators- This Iterator is also known as active iterator or explicit iterator. For this type of iterator the control over iteration of elements is with the programmer. Which means that the programmer define when and how the next element of iteration is called.

Internal Iterators- This Iterator is also known as passive iterator, implicit iterator or callback iterator. For this type of iterator the control over the iteration of elements lies with the iterator itself. The programmer only tells the iterator “What operation is to be performed on the elements of the collection”. Thus the programmer only declares what is to be done and does not manage and control how the iteration of individual elements take place.