Question 3

An array is a data structure that associates integer indexes (in Java, the indexes go from 0 to the one less than the length of the array) with values of a particular type. For example, in Java, a String array associates an integer index with a particular String object.

An associative array is a data type that associates a unique key with a particular value. Unlike an array, the key does not have to be a non-negative integer index. It could be a string, a character, or a number (including negative numbers), as long as the keys are unique values.

What data structure in Java most closely resembles an associative array?

A dequeue -- or double ended queue -- because dequeues are generalizations of queues and stacks, so that you can add and remove elements from either end.

A collection, because it is the most general data structure in the collection framework, and associative arrays are generalizations of arrays.

A map, because the key-value pairs in a map correspond to the key-value pairs in an associative array.

A sorted set, because sets enforce uniqueness of the keys, and the keys should be sorted in an associative array for efficient access.

Question 4

Have you ever seen something like this while watching a video online?

When a video -- or any kind of streaming media -- is buffering, it means that it is preloading data into memory so that it will run smoothly when it is played back on your device.

What data structure is used to implement a buffer?

A set, because the ordering of the blocks of data is not important.

A stack, because the block of data most recently placed on the stack is the first block of data to be removed from the stack.

A list, because blocks of data can be inserted into any position in the list as they arrive.

A queue, because blocks of data are played back from the queue in the same order that they arrive.

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Question 5

According to the module recording, which description best characterizes the representation of a Java LinkedList that has exactly one element.

The representation has one node with a next link and a previous link.

The representation has one node with a single next link.

The representation has two nodes, each with two links: a next link and a previous link. One of the nodes is a sentinel (or dummy) node.

The representation has two nodes, each with a next link. One of the nodes is a sentinel (or dummy) node.

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