# AP Computer Science A Unit 8 Review

AP Computer Science A Unit 8 Review with Java Coding

1. 2D Arrays

2D arrays are data structures that resemble a table arranged with rows and columns. To access each cell, two indices are used: one specifies the row and the other specifies the column.

``````public class TwoDArrayExample {
public static void main(String[] args) {
// Creating a 2D array
int[][] matrix = new int[3][3];

// Initializing the 2D array
matrix[0][0] = 1;
matrix[0][1] = 2;
matrix[0][2] = 3;
matrix[1][0] = 4;
matrix[1][1] = 5;
matrix[1][2] = 6;
matrix[2][0] = 7;
matrix[2][1] = 8;
matrix[2][2] = 9;

// Accessing elements of the 2D array
System.out.println("Element at (1, 1): " + matrix[1][1]); // Output: 5
}
}
``````

2. Traversing 2D Arrays

To traverse 2D arrays, nested `for` loops are used. The outer loop represents the rows, and the inner loop represents the columns.

``````public class TwoDArrayTraversalExample {
public static void main(String[] args) {
// Creating and initializing a 2D array
int[][] matrix = {
{1, 2, 3},
{4, 5, 6},
{7, 8, 9}
};

// Traversing the 2D array
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();
}
}
}
``````

These examples cover the topics of Unit 8 and demonstrate how to create, access, and traverse 2D arrays.