Important Notice:

Practice-It will be discontinued as of November 1st, 2024. After this date, the website will remain online for a transitional period, but login will be restricted to University of Washington NetID authentication. This marks the next phase towards the platform's full retirement. Thank you for your use and support of the application over the years.

If you are looking for an alternative, a similar tool, CodeStepByStep, was developed independently by the original author of Practice-It, and is available at codestepbystep.com**

logo Practice-It logo

Main Page → Problems → Solve a Problem

BJP5 Exercise 10.17: interleave

Language/Type: Java ArrayList Collections
Author: Marty Stepp (on 2019/09/19)

Write a method called interleave that accepts two ArrayLists of integers a1 and a2 as parameters and inserts the elements of a2 into a1 at alternating indexes. If the lists are of unequal length, the remaining elements of the longer list are left at the end of a1. For example, if a1 stores [10, 20, 30] and a2 stores [4, 5, 6, 7, 8], the call of interleave(a1, a2); should change a1 to store [10, 4, 20, 5, 30, 6, 7, 8]. If a1 had stored [10, 20, 30, 40, 50] and a2 had stored [6, 7, 8], the call of interleave(a1, a2); would change a1 to store [10, 6, 20, 7, 30, 8, 40, 50].

Type your solution here:


This is a method problem. Write a Java method as described. Do not write a complete program or class; just the method(s) above.

You must log in before you can solve this problem.


Log In

If you do not understand how to solve a problem or why your solution doesn't work, please contact your TA or instructor.
If something seems wrong with the site (errors, slow performance, incorrect problems/tests, etc.), please

Is there a problem? Contact a site administrator.