Description
This assignment focuses on implementing the methods of a class much like java.util.Arrays. The
Selector.java file defines a class with static methods designed to provide useful functionality on arrays.
Each method of Selector is very clearly specified, is independent of the other methods in the class, and
is designed to provide relatively simple functionality. So, this is a great context for practicing what we are
discussing in lecture – systematic, disciplined development and test-based verification.
The Selector class
You must correctly implement all the method bodies of the provided Selector class. Your implementation
must adhere exactly to the API of the Selector class, as described in the provided source code comments
and as described below.
public final class Selector {
public static int min(int[] a)
public static int max(int[] a)
public static int kmin(int[] a, int k)
public static int kmax(int[] a, int k)
public static int[] range(int[] a, int low, int high)
public static int ceiling(int[] a, int key)
public static int floor(int[] a, int key)
}
The min method.
This method selects the minimum value from a given array. If the array is null or has zero length, this
method throws an IllegalArgumentException. The array is not changed by this method.
Examples:
a[ ] min(a)
[2, 8, 7, 3, 4] 2
[5, 9, 1, 7, 3] 1
[8, 7, 6, 5, 4] 4
[2, 8, 8, 7, 3, 3, 4] 2
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COMP 2210 Fall 2016
The max method.
This method selects the maximum value from a given array. If the array is null or has zero length, this
method throws an IllegalArgumentException. The array is not changed by this method.
Examples:
a[ ] max(a)
[2, 8, 7, 3, 4] 8
[5, 9, 1, 7, 3] 9
[8, 7, 6, 5, 4] 8
[2, 8, 8, 7, 3, 3, 4] 8
The kmin method.
This method selects the k
th minimum value from a given array. A value is the k
th minimum if there are
exactly k − 1 values less than it in the array. If the array is null, has zero length, or if there is no k
th
minimum value, this method throws an IllegalArgumentException. Note that there is no k
th minimum value
if k is less than 1, k is greater than the number of elements in the array, or if k is greater than the number
of distinct values in the array. The array is not changed by this method.
Examples:
a[ ] k kmin(a, k)
[2, 8, 7, 3, 4] 1 2
[5, 9, 1, 7, 3] 3 5
[8, 7, 6, 5, 4] 5 8
[2, 8, 8, 7, 3, 3, 4] 3 4
The kmax method.
This method selects the k
th maximum value from a given array. A value is the k
th maximum if there are
exactly k − 1 values greater than it in the array. If the array is null, has zero length, or if there is no k
th
maximum value, this method throws an IllegalArgumentException. Note that there is no k
th maximum
value if k is less than 1, k is greater than the number of elements in the array, or if k is greater than the
number of distinct values in the array. The array is not changed by this method.
Examples:
a[ ] k kmax(a, k)
[2, 8, 7, 3, 4] 1 8
[5, 9, 1, 7, 3] 3 5
[8, 7, 6, 5, 4] 5 4
[2, 8, 8, 7, 3, 3, 4] 3 4
The range method.
This method returns an array of all values i from a given array such that low ≤ i ≤ high, including duplicate
values. (Note that low and high do not have to be actual values in the given array, and the order of the
resulting values is irrelevant.) The length of the returned array is the same as the number of values i that
meet the criterion. If there are no values i that meet the criterion, this method returns a zero-length array.
If the given array is null or has zero length, this method throws an IllegalArgumentException. The given
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COMP 2210 Fall 2016
array is not changed by this method.
Examples:
a[ ] low high range(a, low, high)
[2, 8, 7, 3, 4] 1 5 [2, 3, 4]
[5, 9, 1, 7, 3] 3 5 [3, 5]
[8, 7, 6, 5, 4] 4 8 [8, 7, 6, 5, 4]
[2, 8, 8, 7, 3, 3, 4] 3 7 [7, 3, 3, 4]
The ceiling method.
This method returns the smallest value i in a given array such that i ≥ key. (Note that key does not have to
be an actual value in the given array.) If the given array is null or has zero length, or if there is no qualifying
value i, this method returns an IllegalArgumentException. The given array is not changed by this method.
Examples:
a[ ] key ceiling(a, key)
[2, 8, 7, 3, 4] 1 2
[5, 9, 1, 7, 3] 7 7
[8, 7, 6, 5, 4] 0 4
[2, 8, 8, 7, 3, 3, 4] 5 7
The floor method.
This method returns the largest value i in a given array such that i ≤ key. (Note that key does not have to
be an actual value in the given array.) If the given array is null or has zero length, or if there is no qualifying
value i, this method returns an IllegalArgumentException. The given array is not changed by this method.
Examples:
a[ ] key floor(a, key)
[2, 8, 7, 3, 4] 6 4
[5, 9, 1, 7, 3] 1 1
[8, 7, 6, 5, 4] 9 8
[2, 8, 8, 7, 3, 3, 4] 5 4
Notes and other requirements
Here are more specific requirements, notes, and suggestions.
• Read this handout carefully. Read the provided source code carefully. Ask questions on Piazza. Start
early and be proactive.
• The constructor has been completed for you and must not be changed in any way.
• You may add any number of private methods that you like, but you may not add any public method
or constructor, nor may you change the signature of any public method or constructor.
• You must not add any fields, either public or private, to the Selector class.
• You must not import anything other than java.util.Arrays. If you do not use java.util.Arrays,
then delete its import statement.
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COMP 2210 Fall 2016
• You are allowed to use sorting only as part of your solution to kmin and kmax. You are not required
to use sorting, but you are allowed to do so for these two methods only.
• Your submission must be solely your own work.
Assignment Submission
You must upload the completed Selector.java file to Web-CAT for grading. Note the following rules
regarding your Web-CAT submissions:
• For each test case that a submission fails, Web-CAT will provide feedback that will allow you to
construct a similar test case for yourself.
• You can submit to Web-CAT no more than ten times for this assignment.
• The last submission that you make to Web-CAT will be used to determine your grade on the assignment, even if its score is lower than that of an earlier submission.
• Submissions made within the 24 hour period after the published deadline will be assessed a late penalty
of 15 points.
• No submissions will be accepted more than 24 hours after the published deadline.
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