1D Arrays - Review

String[] arr1 = new String[6];

boolean[] arr2 = new boolean[2];

1D Arrays - Review

String[] arr1 = new String[6];
arr1[2] = "yay!";

boolean[] arr2 = new boolean[2];
arr2[arr2.length - 1] = true;

2D Arrays

String[][] arr1 = new String[3][5];

2D Arrays

String[][] arr1 = new String[3][5];

​# Rows

​{

2D Arrays

String[][] arr1 = new String[3][5];

​# Rows

​{

​# Columns

2D Arrays

String[][] arr1 = new String[3][5];

​# Rows

​{

​# Columns

Type stored

Initialize arrays with no default values

int[] arr = {5,8,9,4};

Initialize arrays with no default values

int[][] arr = {
{3,4,5},
{6,7,8},
{9,0,1}
};

int[] arr = {5,8,9,4};

Initialize arrays with no default values

int[][] arr = {
{3,4,5},
{6,7,8},
{9,0,1}
};

int[] arr = {5,8,9,4};

int arr[][] = {
{4,3},
{1,8},
{7,9}
};

​I know this looks made up, but it's legit!

Indexing into a 2D array

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

// Print # rows
System.out.println(_________);

// Print # columns
System.out.println(_________);

type[][] name = new type[rows][cols];

Indexing into a 2D array

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

// Print # rows
System.out.println(x.length);

// Print # columns
System.out.println(_________);

type[][] name = new type[rows][cols];

Indexing into a 2D array

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

// Print # rows
System.out.println(x.length);

// Print # columns
System.out.println(x[0].length);

type[][] name = new type[rows][cols];

Predict...

int[][] x = {
{9,8,7},
{6,5,4},
{3,2,1},
{0, -1, -2}
};
System.out.println(x[2][1]);

Predict...

int[][] x = {
{9,8,7},
{6,5,4},
{3,2,1},
{0, -1, -2}
};
System.out.println(x[2][1]);

Predict...

int[][] x = {
{9,8,7},
{6,5,4},
{3,2,1},
{0, -1, -2}
};
System.out.println(x[2][1]);
// Prints 2

Project 8.1 - 8.1.5 Manipulating 2D Arrays

The updateValue method changes the value in arr at [row][col] to value

Call updateValue 3 times

public static void updateValue(int[][] arr, int row, int col, int value)

• Set last value of first array to the length of the entire 2D array.

• Set last value of 2nd array to the total number of values in the entire 2D array.

• Set last value of 3rd array to the sum of the 1st value in 2D array and last value in 2D array.

updateValue(myArray, 1, myArray[0].length-1, 12);

The line above sets the last value of the 2nd array to 12

Project 8.1 - 8.1.6 Complete Chessboard

TODO

• Initialize an 8x8 2D String array

• Add all chess pieces to the board!

  • chess[0][0] = "Rook"; // sets the top left square to "Rook"

Project 8.1 - 8.1.7 TicTacToe

We'll learn this tomorrow!