Important

Question 1

What does map.getOrDefault(k, default v) method do?

Answer 1

If the key exists, returns its value
Otherwise, return the default value

Question 2

What does map.entrySet() do?

Answer 2

Returns the map as a Set view

Ie.,
HashMap: {Top=10, Shoes=20}
Set View: [Top=10, Shoes=20]

Question 3

What does the toArray() method do to a LinkedList?

Answer 3

Converts the Linked List object into an array of object type and returns it

Question 4

How do you check if a map contains a key or a value?

Answer 4

use map.containsKey(k)
or
map.containsValue(v)

Question 5

What does the Hash Map values() method do?

Answer 5

Gets the value set

Question 6

List 11 examples of HashMap methods

Answer 6

put(key, value)
get(key)
getOrDefault(key, defaultValue)
remove(key)

containsKey(key)
containsValue(value)

keySet()
entrySet()

clear()
size()
isEmpty()

Question 7

How do you get the length of a string?

Answer 7

string.length()

Question 8

How do you get a character at a given index of a string?

Answer 8

string.charAt(i)

Question 9

How many ASCII characters are there?

Answer 9

There are 128 ASCII characters, but there is also an extended version of 256 ASCII characters

Question 10

How many letters are in the alphabet?

Answer 10

26

Question 11

How could you find the longest substring without repeated characters?

Question 12

What is the Fibonacci sequence?

Answer 12

Each number is the sum of the 2 preceding numbers starting from 0 and 1

Question 13

What data structure is an efficient way to get a Fibonacci number and why?

Answer 13

Defining a Hash Map outside the method because it can cache the results

public int fib(int n) {
if(n<-1){
return n;
}
if(map.containsKey(n)){
return map.get(n);
} else {
int result = fib(n-1) + fib(n-2);
map.put(n, result);
return result;
}
}