ArrayList Methods Practice

Sample questions

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1. Sample 1difficulty 2/5

   for (int i = 1; i <= list.size(); i++) {
       System.out.println(list.get(i));
   }

   What is the bug?

   • A

     ArrayList lacks a get method

   • B

     Nothing is wrong

   • C

     println cannot accept an Object

   • D

     Indices start at 0 and end at size()-1; should be i = 0; i < list.size()

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   Why

   Java collections are zero-indexed. Starting at 1 skips the first element and going through size() throws IndexOutOfBoundsException.

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2. Sample 2difficulty 2/5

   ArrayList<String> list = new ArrayList<>();
   list.add("a");
   list.add("b");
   list.add("c");
   list.remove(1);
   System.out.println(list.size());

   What is printed?

   • A

     2

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   • B

     1

   • C

     3

   • D

     0

   Why

   Three elements are added, then one is removed. The size is now 3 - 1 = 2.

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3. Sample 3difficulty 2/5

   Get element at index 2 of an ArrayList:

   • A

     list.get(2)

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   • B

     list.at(2)

   • C

     list[2]

   • D

     list.element(2)

   Why

   ArrayList uses methods, not bracket notation.

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4. Sample 4difficulty 2/5

   ArrayList<Integer> list = new ArrayList<>();
   list.add(10);
   list.add(20);
   list.add(30);
   list.add(40);
   int sum = list.get(0) + list.get(list.size() - 1);
   System.out.println(sum);

   What is printed?

   • A

     60

   • B

     30

   • C

     50

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   • D

     100

   Why

   First element 10 plus last element 40 equals 50.

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5. Sample 5difficulty 2/5

   ArrayList<Integer> list = new ArrayList<>();
   list.add(10);
   list.add(20);
   list.add(30);
   list.set(1, 99);
   System.out.println(list.get(1));

   What is printed?

   • A

     30

   • B

     10

   • C

     20

   • D

     99

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   Why

   set(1, 99) replaces the element at index 1 with 99. get(1) returns the new value 99.

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