An algorithm is a detailed, step-by-step set of instructions that solves a problem or completes a defined task. One use of algorithms is to process information contained in data structures (e.g. ArrayLists).
Exmples of algorithms you might need to process the contents of an ArrayList are:
Find the average value in a list of numbers
Count how many names begin with the letter 'A'
Sort a list of numbers into numeric order
Sort a list of names into alphabetic order
There are a number of "standard" algorithms that are used to sort lists. An example of one of these is the bubble sort. Ask your teacher about bubble sorts, or do some research to find out about them on the Internet.
Things to find out before you finish this module:
IntroToJUnitTest
MoreAndMoreTests
Algorithms
SearchingAndSortingAlgorithms