On Making Arrays

How do you create a 1D array?

int[] array = new int[5];

How do you create a 2D array?

int[][] matrix = new int[3][4];

What is the default value of array elements?

0 for numeric arrays, null for objects.

How do you initialize a 1D array with values?

int[] array = {1, 2, 3, 4, 5};

How do you initialize a 2D array with values?

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

How do you fill a 1D array with user input?

for (int i = 0; i < array.length; i++) { array[i] = scanner.nextInt(); }

How do you fill a 2D array with user input?

for (int i = 0; i < matrix.length; i++) { for (int j = 0; j < matrix[i].length; j++) { matrix[i][j] = scanner.nextInt(); }}

How do you iterate through a 1D array to display elements?

for (int i = 0; i < array.length; i++) { System.out.println(array[i]); }

How do you iterate through a 2D array to display elements?

for (int i = 0; i < matrix.length; i++) { for (int j = 0; j < matrix[i].length; j++) { System.out.print(matrix[i][j] + " "); } System.out.println(); }

How do you sum all elements in a 1D array?

int sum = 0; for (int num : array) { sum += num; }

How do you sum all elements in a 2D array?

int sum = 0; for (int i = 0; i < matrix.length; i++) { for (int j = 0; j < matrix[i].length; j++) { sum += matrix[i][j]; }}

How do you get the length of a 1D array?

array.length

How do you get the number of rows in a 2D array?

matrix.length

How do you get the number of columns in a 2D array?

matrix[i].length (for row i).

What is the index range for an array of size 5?

0 to 4.

How do nested loops work for a 2D array?

Outer loop = rows, Inner loop = columns.

What is the default value for uninitialized elements in an array?

0 for numbers, false for booleans, null for objects.

Can arrays hold objects in Java?

Yes.

.length in arrays represents what?

The total number of elements.

What is a ragged array?

A 2D array where rows have different lengths.