Quiz: HashMap and Maps

5 questionsNo time limitPass: 60%+10 XP on first pass

Use HashMap, LinkedHashMap and TreeMap, count frequencies, learn how HashMap works inside (buckets, hashing), the equals/hashCode contract, and Comparable vs Comparator.

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Question 1

What does this print?

import java.util.*;
public class Main {
    public static void main(String[] args) {
        Map<String, Integer> m = new HashMap<>();
        m.put("x", 1);
        m.put("x", 2);
        System.out.println(m.size() + " " + m.get("x"));
    }
}

2 11 22 21 1

Question 2
What is HashMap's default load factor?
0.50.751.00.25
Question 3
If you override equals() in a key class, what else must you override?
toString()hashCode()compareTo()finalize()
Question 4
Which Map keeps its keys sorted?
HashMapLinkedHashMapTreeMapHashtable
Question 5
Which interface lets you define MANY different sort orders outside the class?
ComparableComparatorIterableSerializable