Collections

Question 1

Packages

Answer 1

Packages organize Java classes and create scope to prevent two classes with the same name from having a name collision.

Question 2

Fully qualified Class name

Answer 2

Is the package name along with the class name.

java. util.Scanner in = new 
    java. util.Scanner(System.in);

Question 3

Collections

Answer 3

Are classes in java.util package that define data structures that make working with a set of data easier.
Collections are written to be generic so that they are useful for all reference types.

Question 4

List
List variableName = new ArrayList();

Answer 4

Is an interface, unlike a class contains no code and just creates a data type with guaranteed functionality.

Question 5

Boxing

Answer 5

Boxing is moving a primitive value from the Stack to a Wrapper Class object on the Heap.
Primitive → Wrapper Class

Question 6

Unboxing

Answer 6

Unboxing is moving the value from a Wrapper Class on the Heap to an appropriate primitive value on the Stack.
Wrapper Class → Primitive type

Question 7

Stack

Answer 7

A data structure that organizes data Last In First Out (LIFO). Optimizes Insertion and Deletion, but not possible to search.

Question 8

For each Loop characteristics

Answer 8

1. Loops through each item in a collection or array in order.
2. Cannot modify the collection or array in the loop
3. Does not know the iteration.

Question 9

Queue

Answer 9

A data structure that organizes data First in First Out (FIFO). Optimizes Insertion and Deletion, but not possible to search.

Question 10

List characteristics

Answer 10

1. Maintains the Order of Insertion.
2. Elements can be accessed by index.
3. Allows duplicate elements.
4. Can hold only one data type that is defined by reference type.
5. Can grow and shrink as items are added and removed.
6. An ordered set of elements that is 0-indexed like an array.

Question 11

Stack methods

Answer 11

push( x ) - insert at the beginning of the Stack.
pop() - remove items from the beginning of the Stack.
peek() - to look at the next item without removing it.
isEmpty() - used to determine if the Queue has remaining items.

Question 12

Queue methods

Answer 12

offer( x ) - insert at the end of the Queue
poll() - remove items from the beginning of the Queue
peek() - used to look at the next item without removing it
isEmpty() - used to determine if the Queue has remaining items

Question 13

List variableName = new ArrayList();

Answer 13

Sets the Reference Data Type that the list will hold.

Question 14

ArrayList
List variableName = new ArrayList();

Answer 14

Is a class that implements the List data type, and will be instantiated by the new keyword.

Question 15

List methods

Answer 15

size(), add( x ), add( index, x), get( index ), remove( index )