ArrayList Practice Worksheet

Solutions

Question 1

Step by step:

  1. ["cat"]
  2. ["cat", "dog"]
  3. ["cat", "bird", "dog"]
  4. ["bird", "dog"]
  5. ["bird", "dog", "fish"]
  6. ["dog", "fish"]

Final answer: ["dog", "fish"]

Question 2

Step by step:

  1. [5, 10, 12, 15, 20]
  2. [5, 12, 15, 20]
  3. [3, 5, 12, 15, 20]
  4. [3, 5, 12, 15]
  5. [3, 5, 12, 15, 5]

Final answer: [3, 5, 12, 15, 5]

Question 3

Step by step:

  1. ["red", "blue", "green", "yellow"]
  2. ["red", "purple", "green", "yellow"]
  3. ["red", "purple", "yellow"]
  4. ["red", "orange", "purple", "yellow"]
  5. ["orange", "purple", "yellow"]
  6. ["orange", "purple", "yellow", "orange"]

Final answer: ["orange", "purple", "yellow", "orange"]

Question 4

Step by step:

  1. [2, 4, 6, 8, 10, 12, 14, 3]
  2. After removal loop (removes numbers divisible by 4):
    • When i=1, removes 4
    • When i=3, removes 8
    • When i=5, removes 12
    • Result: [2, 6, 10, 14, 3]
  3. [1, 2, 6, 10, 14, 3]
  4. After doubling loop:
    • Doubles each number
    • Result: [2, 4, 12, 20, 28, 6]

Final answer: [2, 4, 12, 20, 28, 6]

Note for Question 4: This question demonstrates why removing elements while iterating forward through a list can be tricky. After removing 4, the list shifts left, so the next element checked is 10 (not 6). This is why not all multiples of 4 are removed.