Double Dimensional Arrays

Question 1

What is a 2D Array?

Answer 1

It is an array of arrays and it stores data in rows and columns (tabular format).

Question 2

Elements can be accessed through using two indices which is?

Answer 2

row index and column index.

Question 3

What is the other name of 2D dimensional?

Answer 3

multidimensional arrays

Question 4

What is a data structure commonly used in mathematics to represent matrices and complex data structures?

Answer 4

2D Array

Question 5

When a 2D Array is created, Java first creates a 1D array that contains _________ (pointers) to other 1D arrays, which represent the ___ of the 2D array.

Answer 5

references, rows

Question 6

How are the rows of a 2D array stored in Java?

Answer 6

Each row in a 2D array is stored as a separate 1D array, and the main array contains pointers to these individual row arrays.

Question 7

How many indices are required to access an element in a 2D array in Java?

Answer 7

A 2D array in Java requires two indices:
* One for the row
* One for the column

Question 8

How do you initialize a 2D array in Java with specific values?

Answer 8

A 2D array can be initialized using curly braces {} with nested arrays:

int[][] matrix = {
{1, 2, 3},
{4, 5, 6},
{7, 8, 9}
};

Question 9

How do you declare a 2D array in Java?

Answer 9

Declared using the following syntax:
dataType[][] arrayName;

Question 10

What are the ways to initialize a 2D Array

Answer 10

1. Static Initialization
2. Dynamic Initialization

Question 11

Set the size first, then assign values later

Answer 11

Dynamic Initialization

Question 12

Assign values directly during declaration.

Answer 12

Static Initialization

Question 13

What happens when only the number of rows is specified while declaring a 2D array in Java?

Answer 13

The columns remain uninitialized, creating a jagged array where each row can have a different number of columns.

Question 14

A ____ array is useful for storing ____________ , such as words of different lengths, lists of varying sizes, or ____________.

Answer 14

jagged, flexible data structures, irregularly shaped matrices

Question 15

Why must the number of rows be specified first when creating a 2D array in Java?

Answer 15

In Java, a 2D array is an array of 1D arrays, so the number of rows must be specified first to allocate space for row references before defining column sizes.

Question 16

What happens when a 2D array is declared without initializing rows or columns in Java?

Answer 16

It only creates a reference without allocating memory. The array must be initialized before use.

Question 17

How do you declare a 2D array in Java without initializing its size?

Answer 17

You can declare a 2D array like this:
int[][] matrix;

Question 18

This is capable of storing images, text, and other types of data, and is useful for data analysis and visualization?

Answer 18

2D Array

Question 19

Specify the number of rows but leave columns uninitialized.

Answer 19

Double-Dimensional Array with Only Rows Initialized

Question 20

What is a jagged Array?

Answer 20

is a 2D array where each row can have a different number of columns.

Question 21

You must define rows first because a 2D array is an array of arrays.

Answer 21

Double-Dimensional Array with Only Columns Initialized

Question 22

This type of array can declare a 2D array without initializing rows or columns.

Answer 22

Double-Dimensional Array with No Rows or Columns Initialized

Question 23

This is just a reference; no memory is allocated yet and must be initialize before use.

Answer 23

Double-Dimensional Array with No Rows or Columns Initialized

Question 24

This type of array can declare a 2D array without initializing rows or columns.

Answer 24

Double-Dimensional Array with No Rows or Columns Initialized

Question 25

Where do 2D arrays are usually stored?

Answer 25

Often stored in memory as 1D arrays.

Question 26

What are the 2 common methods for storing 2D array data?

Answer 26

*Row-Major Order. *Column-Major Order.

Question 27

How does Row-Major Order work?

Answer 27

All elements of the first row are stored consecutively. Followed by all elements of the second row, and so on.

Question 28

What type languages that uses Row-Major Order?

Answer 28

Used in languages like C, C++, and Java.

Question 29

In Row-Major Order, Elements are stored ______ by _____ in memory.

Answer 29

row by row

Question 30

How does Column-Major Order work?

Answer 30

All elements of the **first column** are stored consecutively. Followed by all elements of the second column, and so on.

Question 31

In Column-Major Order, Elements are stored ______ by _____ in memory.

Answer 31

column by column

Question 32

What type languages that uses Column-Major Order?

Answer 32

Used in languages like Fortran, MATLAB, and R.

Question 33

What are the key major differences between Row-Major and Column-Major?

Answer 33

Row-Major fills rows first, while Column-Major fills columns first

Question 34

Arrays are stored in contiguous ________ ________.

Answer 34

memory locations

Question 35

Elements are accessed using ______ _______.

Answer 35

numeric indexing

Question 36

What is the syntax for accessing elements?

Answer 36

DataType var = ArrayName[i][j]

Question 37

What is a heterogeneous 2D array?

Answer 37

Where each row can store different data types.

Question 38

What does homogenous mean in 2D Array?

Answer 38

Homogeneous means that all elements in an array must be of the same data type.

Question 39

What does Heterogeneity mean in 2D Array?

Answer 39

The presence of different types or variations within a group.

Question 40

Java arrays are ________ by _______(all elements must be of the same type).

Answer 40

homogeneous, default

Question 41

How can heterogeneity be achieved in a Java 2D array?

Answer 41

It can be achieved by using the Object class, which is the root of Java’s class hierarchy. By declaring a 2D array as Object[][], we can store elements of different data types.

Question 42

How do you declare and initialize a heterogeneous 2D array in Java?

Answer 42

Use Object[][], which allows storing different data types.

Question 43

How to access 2D Array Elements?

Answer 43

You must cast(typecasting) elements back to their original types when accessing them.

Question 44

Arrays know their ______ (how many elements they can store).

Answer 44

length

Question 45

The _______ is a public ______ so you can use _______ to access the field (arrayName.length).

Answer 45

length, read-only field, dot-notation

Question 46

Gives the number of rows in the 2D array.

Answer 46

numbers.length

Question 47

square matrix

Answer 47

(rows = columns)

Question 48

Gives the number of columns in the first row.

Answer 48

numbers[0].length

Question 49

What type of Loop to use in 2D Array?

Answer 49

nested loops

Question 50

What does traverse mean in 2D Array?

Answer 50

Traverse means to go through or visit each element of a data structure one by one.

Question 51

What are the Key points when using Row-Major and Colum-Major?

Answer 51

Row-Major Order: *More efficient in Java. *Outer loop iterates over rows, inner loop iterates over columns. Column-Major Order: *Useful for specific use cases. *Outer loop iterates over columns, inner loop iterates over rows.

Question 52

Enhanced For Loop with 2D Arrays Uses ________ and always iterates in ______ order.

Answer 52

nested enhanced for loops, row-major

Question 53

When using enhanced for loop. The out loop access the ____ as an _____. While the Inner loop access each _________ in the row.

Answer 53

row, array, element

Question 54

What are the common mistakes/issues with 2D Arrays?

Answer 54

* Incorrect Array Indexing * Assuming Rectangular Arrays * Forgetting to Initialize Rows * Confusing Row-Major and Column-Major Order

Question 55

A double-dimensional (2D) array is a ________ that stores elements in a ______ format with rows and columns, allowing for the organization of data in a _______ manner.

Answer 55

data structure, tabular, grid-like

Question 56

In Java, a 2D array is essentially an _________, where each row is a _________ array, and elements are accessed using ________: one for the row and one for the column.

Answer 56

array of arrays, one-dimensional, two indices

Question 57

2D arrays can be ________ (all rows have the same number of columns) or _______ (rows can have varying lengths).

Answer 57

rectangular, jagged

Question 58

They are commonly used to represent matrices, tables, or grids in applications like _________, _________, and _________.

Answer 58

image processing, game development, data analysis

Question 59

Key operations include _______ , _______ (statically or dynamically), _______ (using nested loops in row- major or column-major order), and _______ elements using indices.

Answer 59

declaration, initialization, traversal, accessing