Test Writing: Count Letters with Map

Created By: Geoffrey Challen

/ Version: 2020.10.0

Create a public class CountLetters providing a single static method countLetters. countLetters accepts an array of Strings and returns a Map from Strings to Integers. (You can reject null arguments using assert.)

The map should contain counts of the passed Strings based on their first letter. For example, provided the array {"test", "me", "testing"} your Map should be {"t": 2, "m": 1}. You should ignore empty Strings and not include any zero counts.

As a reminder, you can retrieve the first character of a String as a char using charAt. You may find substring more helpful. You may also want to examine the Map getOrDefault method. You can use any Map implementation in java.util.

Test Design Challenge

You're challenge is to write tests for this problem described above.

• Provide a public class named TestCountLetters with a single non-private class method named test that accepts no arguments and does not return a value.
• If the implementation of the class described above is incorrect, your test method should throw an exception.
• If it is correct, do not throw an exception.
• You may want to use Java's assert method