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Lab4 Loops and Arrays

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EECS1022 (M,N,O)
Lab4
Loops and Arrays

• To complete this lab, it is strictly forbidden for you to use any library class (e.g., ArrayList).
Violating this requirement will cause a 50% penalty on your lab marks.
• For this lab, you will be graded not only by JUnit tests given to you, but also additional
tests covering some other input values. This is to encourage you to take more responsibility
for the correctness of your code, by writing your own tests.
• Your lab assignment is not graded during the weekly scheduled lab sessions.
– Follow the instructions to submit (via eClass) the required file(s) for grading.
– There are three submission links: two of them are for late submissions only. If you
already submit before the original deadline, do not make any more submissions, as the
later submission (with a penalty) will be graded.
– Emailing your solutions to the instructor or TAs will not be acceptable.
• Texts in blue are hyperlinks to the corresponding documents/recordings.

Contents
1 Task 1: Complete Weekly Java Tutorial Videos 4
2 Task 2: Complete Programming Exercises 5
2.1 Step 1: Download and Import the Starter Project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2 Step 2: Programming Tasks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.2.1 Method to Implement: getMultiplesOf3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.2.2 Method to Implement: getFilteredSeq . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.2.3 Method to Implement: getAllPrefixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2.4 Method to Implement: getGroupedNumbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.3 Step 3: Exporting the Completed Project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3 Submission 12
4 Amendments 13
Learning Outcomes
By completing the assigned exercises of this lab, you are expected to be able to:
1. Exercise a simple workflow of Github.
2. In the Eclipse IDE (Integrated Development Environment):
• Import a starter project archive file.
• Given a computational problem, develop a Java solution (i.e., a utility method) composed of:
– Numerical Literals and operators
– String Literals and operators
– Variables and assignments
– (Nested) Selections/Conditionals/If-Statements
– Loops (for-loop vs. while-loop)
– Arrays
• Run a Java class with with the main method as a console Java application.
• Use the given JUnit tests (calling the utility methods) to guide the development.
• Use the debugger features (step over/into/out/return) to find defects in programs.
• Export an existing project as an archive file.
3. Understand the separation of concerns (using packages): model, console apps, and junit tests.
2
Assumptions
• You have already setup a Github account and stored work in a private repository: EECS1022-W21-workspace.
Note. You only submit your lab through eClass, not Github. Though not required, it is highly recommended
that you adapt to the practice of backing your work using a versioning tool like Github.
• You are able to use Eclipse to complete the tutorial videos and this lab assignment on either your own machine
or the EECS remote labs.
Note. The starter project was created using Eclipse and an Eclipse project archive file is expected to be
submitted. Therefore, you may not want to use other IDE such as IntelliJ.
Requirements of this Lab
• For this lab, you will be graded not only by JUnit tests given to you, but also additional tests covering
some other input values. This is to encourage you to take more responsibility for the correctness of your code,
by writing your own tests.
• To complete this lab, it is strictly forbidden for you to use any library class (e.g., ArrayList). Violating
this requirement will cause a 50% penalty on your lab marks.
• The grading of your lab will start by automatically unzipping the submitted Java project archive file (.zip)
and extracting the required class(es). It is therefore crucial for you to follow precisely the spelling of the
archive file name. Penalty will be taken if the grading cannot proceed due to carelessness on following the
instructions in Section 2.3.
• Your lab submission will only be graded using JUnit (for this lab, the tests supplied to you plus some
additional tests). That is, your lab submission will not be graded manually using the console application
given to you.
• For the JUnit test class TestUtilities.java given to you:
– Do not modify the test methods given to you.
– You are allowed to add new nest methods.
• Do not modify the console application class (in package console apps) given to you.
• For each utility method in the Utilities class that you are assigned to implement, as discussed in Part F
of Week 1’s Java tutorial videos:
– No System.out.println statements should appear in each of the utility method.
Instead, an explicit, final return statement is placed for you.
– No Scanner operations (e.g., input.nextInt()) should appear in each of the utility method.
Instead, refer to the input parameters of the method.
• You are welcome to ask questions related to this lab or the assigned tutorial videos on the forum. However,
please be cautious:
– You can help your fellow students understand the requirements of tasks.
– Do not share the code you developed to ask, or to answer, questions.
∗ Questions specific to the code you write would be best and most effectively addressed by TAs (during
scheduled labs) or your instructor (during office hours or appointments).
∗ Week 2’s tutorial videos (Parts C to E) introduce to you debugger in Eclipse. You are encouraged
to set breakpoints and launch the debugger when you are stuck at your own program.
– Hints on how the solution should look like are left only to the instructors who moderate the forum.
3
1 Task 1: Complete Weekly Java Tutorial Videos
• For Lab4, you are assigned to study Week 5 Part A to Part D of the Java tutorial series:
https://www.youtube.com/playlist?list=PL5dxAmCmjv_7Ri55ckAVTx0IbtcJEqzz8 [ Week 5 only ]
To reference tutorial videos from the previous weeks, see:
https://www.youtube.com/playlist?list=PL5dxAmCmjv_6wy2m0yq2wObIWPz4tAxW6 [ All Weeks ]
These Java tutorial videos assigned to you are meant for you to:
1. Obtain extra hands-on programming experience on Java, supplementing your weekly lectures.
2. Complete the lab assignment with the necessary skills and background.
Though we do not require the submission of the weekly Java tutorial project (like in Lab0), examples and
insights discussed in these tutorials will be covered in your (written and programming) tests
and exam: should you decide to skip the weekly tutorial videos, it would be your choice.
As you study through the example Java classes in the tutorial videos, you are advised to type them out
(but absolutely feel free to add new Java classes to experiment) on Eclipse.
• You can find the iPad notes of illustrations from the tutorial videos here:
https://www.eecs.yorku.ca/˜jackie/teaching/tutorials/notes/EECS1022%20Tutorial%20on%20Java.pdf
Getting Prepared for Programming Test 2
• Your Programming Test 2 (shortly after the reading week) will cover loops and arrays.
• Three sets of practice test questions are available on the M,N,O eClass site (under the Practice Programming
Tests section).
Here is a tutorial series on the solution to each question:

• You may consider tackling some of the practice tests, which will help you complete the lab exercises.
4
2 Task 2: Complete Programming Exercises
Starting Task 2 should mean that you have already completed the weekly Java tutorial videos (Section 1).
2.1 Step 1: Download and Import the Starter Project
1. Download the Eclipse Java project archive file from eClass: EECS1022 W21 Lab4.zip
2. Launch Eclipse and browse to EECS1022-W21-workspace as the Workspace then click on Launch, e.g.,
3. In Eclipse:
3.1 Choose File, then Import. 3.2 Under General, choose Existing Projects into Workspace.
3.3 Choose Select archive file. Make sure that the EECS1022 W21 Lab4 box is checked under Projects.
Then Finish.
5
2.2 Step 2: Programming Tasks
From the Package Explorer of Eclipse, your imported project has the following structure.
• You can manually test the assigned methods using the corresponding console application classes in package
console apps. These classes are completed and given to you. See below for more descriptions.
• Your goal is to pass all JUnit tests given to you (i.e., a green bar). To run them, as shown in the Java
tutorials on Week 1, right click on TestUtilities.java and run it as JUnit tests. Of course, none of the
given tests would pass to begin with.
You must not modify these given JUnit tests.
How to Deal with a Failed JUnit Test? From the JUnit panel from Eclipse, click on the failed test, then
double click on the first line underneath Failure Trace, then you can see the expected value versus the return
value from your utility method.
6
2.2.1 Method to Implement: getMultiplesOf3
Problem. You are asked to implement a utility method which takes as input an array of integers and returns
another array containing all those elements that are multiples of 3. For example, if the input array is:
<2, 1, 6, 5, 4, 3>
Then the output or returned array is:
<6, 3>
Note that the length of the output array corresponds the number of elements in the input array that are multiples
of 3, meaning that if the input array is empty, or if there are no multiples of 3 in the input array, then the output
array should be empty.
Also, the output array should preserve the order in which these multiples, if any, appear in the input array. For
example, in the above example, multiples of 3 in the input array appear in the order of 6 followed by 3, which is
reflected in the output array.
Testing. Your goal is to first pass all tests related to this method in the JUnit test class TestUtilities. You
are encouraged to write additional JUnit tests. These tests document the expected values on various
cases: study them while developing your code.
However, use the console application class GetMultiplesOf3App if you wish (e.g., use the input and expected
values from the JUnit tests). Here is an example run:
How many numbers do you want to input?
10
Enter input 1:
89
Enter input 2:
23
Enter input 3:
42
Enter input 4:
87
Enter input 5:
18
Enter input 6:
36
Enter input 7:
23
Enter input 8:
97
Enter input 9:
102
Enter input 10:
987
<42, 87, 18, 36, 102, 987>
Todo. Implement the Utilities.getMultiplesOf3 method. See the comments there for the input parameters
and requirements.
7
2.2.2 Method to Implement: getFilteredSeq
Problem. You are asked to implement a utility method which takes as input an array (say numbers) of integers
and an integer (say n). Note that n may or may not exist in numbers. The utility method returns another array
containing all elements in numbers that are not equal to n. For example, if the input n is 3 and the input array
numbers is:
<3, 1, 2, 3, 4>
Then the output or returned array is:
<1, 2, 4>
Note that the length of the output array corresponds the number of elements in the input array that are not equal
to n, meaning that if the input array is empty, or if n does not exist in the input array, then the output array
should be just the same as the input array.
Also, the output array should preserve the order in which elements appear in the input array. For example, in
the above example, elements in the output array appear in the order of 1 followed by 2 and then by 4, which is
reflected in the input array.
Testing. Your goal is to first pass all tests related to this method in the JUnit test class TestUtilities. You
are encouraged to write additional JUnit tests. These tests document the expected values on various
cases: study them while developing your code.
However, use the console application class GetFilteredSeqApp if you wish (e.g., use the input and expected
values from the JUnit tests). Here is an example run:
How many numbers do you want to input?
5
Enter input 1:
3
Enter input 2:
1
Enter input 3:
2
Enter input 4:
3
Enter input 5:
4
Which number do you wish to filter from the input numbers?
3
<1, 2, 4>
Todo. Implement the Utilities.getFilteredSeq method. See the comments there for the input parameters
and requirements.
8
2.2.3 Method to Implement: getAllPrefixes
Problem. You are asked to implement a utility method which takes as input an array of integers and returns
another array of strings, each of which denoting a non-empty prefix of the input array. For example, if the input
array is:
<3, 1, 4>
Then the output or returned array of string values is:
<“[3]”, “[3, 1]”, “[3, 1, 4]”>
Note that the length of the output array is equal to the length of the input array. Also, elements in the output
array are “sorted” by the lengths of the prefixes (e.g,. the first element is the prefix of length 1, the second element
is the prefix of length 2).
Testing. Your goal is to first pass all tests related to this method in the JUnit test class TestUtilities. You
are encouraged to write additional JUnit tests. These tests document the expected values on various
cases: study them while developing your code.
However, use the console application class GetAllPrefixesApp if you wish (e.g., use the input and expected
values from the JUnit tests). Here is an example run:
How many numbers do you want to input?
5
Enter input 1:
3
Enter input 2:
1
Enter input 3:
4
Enter input 4:
2
Enter input 5:
5
<[3], [3, 1], [3, 1, 4], [3, 1, 4, 2], [3, 1, 4, 2, 5]>
Todo. Implement the Utilities.getAllPrefixes method. See the comments there for the input parameters
and requirements.
9
2.2.4 Method to Implement: getGroupedNumbers
Problem. You are asked to implement a utility method which takes as input an array of integers and returns
another array grouping all elements from the input array as follows, from left to right: 1) elements divisible by
3; 2) elements divided by 3 with the remainder 1; and 3) elements divided by 3 with the remainder 2. For example,
if the input array is:
<2, 4, 6, 5, 1, 3>
Then the output or returned array is:
h 6, 3
| {z }
Group 1
, 4, 1
| {z }
Group 2
, 2, 5
| {z }
Group 3
i
Note that the input and output arrays are equally long, meaning that if the input array is empty, then the output
array should be empty.
Also, each group of the output array should preserve the order in which its elements appear in the input array.
For example, in the above example, Group 2 of the output array (i.e., those divided by 3 with the remainder 1)
contains 4 followed by 1, reflecting their order in the input array.
Testing. Your goal is to first pass all tests related to this method in the JUnit test class TestUtilities. You
are encouraged to write additional JUnit tests. These tests document the expected values on various
cases: study them while developing your code.
However, use the console application class GetGroupedNumbersApp if you wish (e.g., use the input and expected
values from the JUnit tests). Here is an example run:
How many numbers do you want to input?
10
Enter input 1:
89
Enter input 2:
22
Enter input 3:
42
Enter input 4:
87
Enter input 5:
19
Enter input 6:
36
Enter input 7:
23
Enter input 8:
97
Enter input 9:
102
Enter input 10:
987
<42, 87, 36, 102, 987, 22, 19, 97, 89, 23>
Todo. Implement the Utilities.getGroupedNumbers method. See the comments there for the input parameters
and requirements.
10
2.3 Step 3: Exporting the Completed Project
You are required to submit a Java project archive file (.zip) consisting all subfolders.
In Eclipse:
1. Right click on project EECS1022 W21 Lab4. 2. Under General, choose Archive File.
Then click Export
3. Check the top-level EECS1022 W21 Lab4
Make sure that all subfolders are checked: .settings, bin, and src.
Under To archive file: browse to, e.g., desktop, and save it as EECS1022 W21 Lab4.zip (case-sensitive)
Then Finish.
Note. In case you have concerns about exporting and submitting the .setting subfolder: it will be kept
confidential and access-protected on eClass.
11
3 Submission
1. Before you submit, you must make sure that the Problems panel on your Eclipse shows no errors (warnings
are acceptable). In case you do not see the Problems panel: click on Window, then Show View, then Problems.
Submitting programs with errors (meaning that it cannot be run for grading) will result in
possible partial, but low, marks.
2. Section 2.3 asks you to export the Java project as an archive file:
EECS1022 W21 Lab4.zip
Before you submit, verify that its unzipped version has the following structure:
Figure 1: Lab4 Expected Project Structure
3. Go to the eClass site for Sections M,N,O: https://eclass.yorku.ca/eclass/course/view.php?id=6214
4. Under the Lab Submissions section, click on Lab4 to submit the Java archive file: EECS1022 W21 Lab4.zip
• You may upload as many draft versions as you like before the deadline.
• You must explicitly submit the draft version for grading before the deadline.
• Once you click on the submit button, you can no longer upload another draft version.
12
4 Amendments
Clarifications or corrections will be added to this section.

13

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