Description
• When submitting modifications of existing code, please do not reformat any sections of
the code that you did not explicitly have to change. We need to be able to diff your
submission against the original to see exactly what was changed.
• Submit an archive on Canvas containing all classes originally posted as hw3.zip.
1) Implement hw4.subsetsum.findSubsetSumFJ so that it uses the Fork-Join framework to
recursively parallelize the sequential version findSubsetSum. The student paper and sample
code on this topic can be found on Canvas. In addition, you can find an implementation of
merge sort using Fork-Join in the sample code. The tutorial from Oracle might be helpful too.
https://docs.oracle.com/javase/tutorial/essential/concurrency/forkjoin.html and this example
might also be useful:
https://homes.cs.washington.edu/~djg/teachingMaterials/spac/grossmanSPAC_forkJoinFramework.html
2) Some fun exercises using Java streams. The student papers are available on Canvas. In
addition, you’ll likely need to refer to:
• the API for java.util.stream.Stream and java.util.stream.IntStream
• the API for java.util.stream.Collectors, which has a number of examples similar to
part (b)
• The tutorial on reduction here, which is the example to follow for part (c)
https://docs.oracle.com/javase/tutorial/collections/streams/reduction.html
There are also two excellent introductory articles provided by Oracle:
• https://www.oracle.com/technetwork/articles/java/ma14-java-se-8-streams-2177646.html
• https://www.oracle.com/technetwork/articles/java/architect-streams-pt2-2227132.html
All the methods in (a) and (b) should be implemented as one liners, using the general form
return something.stream()
.blah(…)
.blah(…)
.blah(…)
.blah(…);
a) See hw4.employees.StreamTest. Write the method
public static int[] evensToFront(int[] arr)
that, given an integer array, returns a new array with the even numbers in the front and the odd
numbers at the end. The relative ordering within the evens and the odds is not changed. (Tip: you
can us the .boxed() method on an IntStream to get a stream of Integers, and then use
.sorted() with a custom comparator.)
b) The remaining stream problems are methods of the class EmployeeDatabase. See the javadoc
in that class for details. There are some snippets of test code in EmployeeTest. There are five
methods to implement.
averageSalaryForDepartment
averageSalariesByDepartment
listOfEmployeesInProduction
getHighestPaidEmployees
listEmployeesByPosition
c) Implement the class PositionLister (a nested class within EmployeeDatabase). After this,
the method listEmployeesByPositionAlt should work correctly. Be sure to try it for a
parallel stream too!