Here’s how you can convert this information into flashcards. Each card contains a concise question and answer for quick recall.

Flashcards: Array Basics

Q: How do you create a 1D array?
A: int[] array = new int[5];

Q: How do you create a 2D array?
A: int[][] matrix = new int[3][4];

Q: What is the default value of array elements?
A: 0 for numeric arrays, null for objects.

Flashcards: Array Initialization

Q: How do you initialize a 1D array with values?
A: int[] array = {1, 2, 3, 4, 5};

Q: How do you initialize a 2D array with values?
A:

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

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

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

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

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

Flashcards: Iteration

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

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

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

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();
}

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

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

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

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

Flashcards: Array Properties

Q: How do you get the length of a 1D array?
A: array.length

Q: How do you get the number of rows in a 2D array?
A: matrix.length

Q: How do you get the number of columns in a 2D array?
A: matrix[i].length (for row i).

Q: What is the index range for an array of size 5?
A: 0 to 4.

Flashcards: Nested Loops for 2D Arrays

Q: How do nested loops work for a 2D array?
A: Outer loop = rows, Inner loop = columns.

for (int i = 0; i < matrix.length; i++) {
    for (int j = 0; j < matrix[i].length; j++) {
        // Access element at [i][j]
    }
}

Flashcards: Key Concepts

Q: What is the default value for uninitialized elements in an array?
A: 0 for numbers, false for booleans, null for objects.

Q: Can arrays hold objects in Java?
A: Yes.

Q: What does .length represent for an array?
A: The total number of elements.

Q: What is a ragged array?
A: A 2D array where rows have different lengths.