Unit 4: Data Collections
CS A · Unit 4 · Paper 3

Data Collections unit test

A test on this unit alone, marked as a percentage and a letter grade — for the test your class is actually sitting, rather than for May. Answer everything, then submit once: seeing the answer to question 3 before attempting question 4 makes the final percentage meaningless.

Paper 1Paper 2Paper 3
Each paper is built from this unit’s 63 terms and is the same for everyone, so a teacher can assign “Unit 4, Paper 3” and every student sits the identical test. Multiple choice is marked objectively; the written sections you mark yourself against the model answer and rubric.
Suggested time 33 min 30 points0/17 attempted
1

Standard algorithm: shift elements left

2

Array indexing

3

Efficiency of insertion into an ArrayList

4

Array

5

Swapping two elements

6

Looping backward to remove safely

7

ArrayList of objects

8

Standard algorithm: count elements meeting a condition

9

Why merge sort is faster on large arrays

10

2D array

11

Removing all matching elements

12

Building a String in a loop

Short answer 1. Define or explain: Comparing objects in a collection

3 pts

Short answer 2. Define or explain: Off-by-one in array bounds

3 pts

Short answer 3. Define or explain: Array of objects

3 pts

Short answer 4. Define or explain: Declaring an ArrayList

3 pts

Free response

6 pts

This course has no free-response prompt tagged to this unit, so one from elsewhere in the course is used. It is still worth writing — the skill transfers.

A 2D int array grid represents daily rainfall readings; each row is one week and each column is one day. Write two static methods. (a) public static int rowTotal(int[][] grid, int row) — returns the sum of the values in the given row. (b) public static int driestWeek(int[][] grid) — returns the index of the row with the smallest total. If two rows tie, return the lower index. Assume grid has at least one row and that all rows have the same length. Method (b) should call method (a).