How to declare/initialize 2D arrays

// Boiler Plate Code public class Main { public static void main(String[] args) {

    */ (Intialize Array Here) */

    // Display Array Code below
    for(int i = 0; i < myArray.length; i++) {
        for (int j = 0; j < myArray[i].length; j++) {
            System.out.print(myArray[i][j] + " ");
        }
        System.out.println();
    }
} }

Main.main(null) 1) All in one

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

2) Empty array and manual input with indexes

// Declare a 3x3 empty 2D array
int[][] matrix = new int[3][3];

// Assign values to the 2D array using indexes
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;

3) Nested For-Loop

int value = 1; // Start value
for (int i = 0; i < matrix.length; i++) {  // Outer loop for rows
    for (int j = 0; j < matrix[i].length; j++) {  // Inner loop for columns
        matrix[i][j] = value++; // Assign value and increment
    }
}

Popcorn Hack 1 (Part 1):

  • Intialize a 2D array of the people in your group grouped based on pairs with 3 different methods
  • ex Array: [[Anusha, Vibha],[Avanthika, Matthew]]

String[][] method1 = {
    {"Tarun", "Jon"},
    {"Srijan", "Ian"}
};

String[][]method2=new String[2][2];
method2[0][0]="Tarun";
method2[0][1]="Jon";
method2[1][0]="Srijan";
method2[1][1]="Ian";


String[]names={"Tarun","Jon","Srijan","Ian"};
String[][]method3=new String[2][2];
int i=0;
int j=0;
for(int index=0;index<names.length;index++){
    method3[i][j]=names[index];
    j+=1;
    if(j==2){
        j=0;
        i+=1;
    }
}
System.out.println(Arrays.deepToString(method1));
System.out.println(Arrays.deepToString(method2));
System.out.println(Arrays.deepToString(method3));


[[Tarun, Jon], [Srijan, Ian]]
[[Tarun, Jon], [Srijan, Ian]]
[[Tarun, Jon], [Srijan, Ian]]