Maps (aka Dictionaries)

Reading

• Please read about Map and HashMap.
• You do not need to do the programming exercises in the reading, but you may find it helpful to try them a little. It’s up to you.

Important concepts

• Map data structure (also called a dictionary or associative array in other languages)
• keys vs values, key-value pair

Things to consider (exercises for yourself, not to turn in)

• The Java Map interface has the get() method for looking up the value that corresponds to a given key. Why isn’t there a method that goes in the other direction, i.e. looking up the key that corresponds to a given value?
• Is there a situation where containsKey(x) could return true, but then get(x) returns null? (Yes! What is it?)

Your response

What do you hope to learn about maps from the in-class activity?