3.7. Exercises: Control Flow and Collections¶
Work on these exercises in the IntelliJ
creating a new class for each item. You may call these classes whatever you
like, but remember to use the proper
Java naming conventions.
3.7.1. Array Practice¶
Create and initialize an array with the following values in a single line:
1, 1, 2, 3, 5, 8.
Loop through the array and print out each value, then modify the loop to only print the odd numbers.
For this exercise, use the string
I would not, could not, in a box. I would not, could not with a fox. I will not eat them in a house. I will not eat them with a mouse.Use the
splitmethod to divide the string at each space and store the individual words in an array. If you need to review the method syntax, look back at the String methods table.
Print the array of words to verify that your code works. The syntax is:
Repeat steps 3 and 4, but change the delimiter to split the string into separate sentences.
Some characters, like a period
".", have special meanings when used with
split method. They cannot be used as-is for the deliminator.
To use these characters as the deliminator, we must escape their special
meanings. Instead of
.split("."), we need to use
3.7.2. ArrayList Practice¶
Write a static method to find the sum of all the even numbers in an ArrayList. Within
main, create a list with at least 10 integers and call your method on the list.
Write a static method to print out each word in a list that has exactly 5 letters.
Modify your code to prompt the user to enter the word length for the search.
BONUS: Instead of creating our own list of words, what if we want to use the string from the Array Practice section? Search “Java convert String to ArrayList” online to see how to split a string into the more flexible
3.7.3. HashMap Practice¶
Make a program similar to
GradebookHashMap that does the following:
It takes in student names and ID numbers (as integers) instead of names and grades.
The keys should be the IDs and the values should be the names.
Modify the roster printing code accordingly.