How to make a knight randomly move in a chessboard?

I have this program called knight tour where the knight moves around a chess board. I have been trying to figure out how to make the knight move randomly, instead of following a pattern.

I would like to know how to randomly move the knight.

Here's my code:

package assignment3;
import java.util.Random;
/*
* knows its current position (row and column) 
* knows the eight types of moves it can make
* can tell you it’s current row and column
* can determine whether a move of a given type is legal or not
* can move
*/
public class Knight {
private int boardSize = 8;
private int[] rowMoves = {-1, -2, -2, -1, 1, 2, 2, 1};
private int[] colMoves = {2, 1, -1, -2, -2, -1, 1, 2};
public Knight() {
//ignore this constructor
}
public void InitializeBoard() {
//initialize board
for (int i = 0; i < boardSize; i++)
Arrays.fill(chessboard2[i], Integer.MIN_VALUE); //setting array to negative value
}
/**
* calls method canMove to check if knight can move
* moves knight
*/
public boolean move(int moveNum, int x, int y, int[][] chessboard2) {
Random rand = new Random(); 
//if moveNum == 64 all squares have been visited 
if (moveNum == 64) {
System.out.println("\ntrue board is 64\n");
return true;
}
//int nextRow = rand.nextInt(boardSize);
//int nextCol = rand.nextInt(boardSize);
//for loop to try 8 possibe moves
for (int i = 0; i < rowMoves.length; i++) {
int nextRow =  x + rowMoves[i];
int nextCol =  y + colMoves[i];
//check if postion is valid and not visited yet
if (canMove(nextRow, nextCol) && chessboard2[nextRow][nextCol] == Integer.MIN_VALUE) {
//if move is valid knight moves
chessboard2[nextRow][nextCol] = moveNum + 1;
//make next move
if(move(moveNum + 1, nextRow, nextCol, chessboard2))
return true;
//move(moveNum + 1, nextRow, nextCol);
//if cant find next move: backtrack
chessboard2[nextRow][nextCol] = Integer.MIN_VALUE;
}
}
return false;
}     
/**
* calls method moveLegal from class Chessboard to see if move is legal
* @return true if move is legal, else return false
*/
public boolean canMove(int x, int y) {
//if statement to check if currentRow and currentCol is whithin 
//boundaries
return(x >= 0 && x < boardSize && y >= 0 && y < boardSize);
}
public void print() {
for (int i = 0; i < boardSize; i++)
System.out.println(String.join(" ", chessboard2[i]));
}
public void solve() {
//setting array location [0][0] to 0
chessboard2[0][0] = 1;
//check move
if (move(1, 0, 0)) // if true, it will print chess board
print();
else //if false, there is no solution
System.out.print("no solution");
}
}
public class TesterMain {
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
Knight test = new Knight();
test.solve();
}
}

Sorry if my code is a bit messy, I am still working on the program.

The easiest way to randomise your move is to create a list of valid moves for a given position of the knight and then select one at random. List and Random APIs go hand in hand:

//List<Integer> moves = ...
int move = moves.get(new Random().nextInt(moves.size()));

Restructuring your move method to something like this should do the job:

public boolean move(int moveNum, int x, int y, int [][] chessboard2) {
// 1. List all valid moves
List<Integer> validMoves = new ArrayList<Integer>();
//for loop to try 8 possibe moves
for(int i = 0; i < rowMoves.length; i++) {
if (
canMove(x + rowMoves[i], y + colMoves[i])
&& chessboard2[x + rowMoves[i]][y + colMoves[i]] == Integer.MIN_VALUE
) {
validMoves.add(i);
}
}
// 2. Try to make the move if any available
if (validMoves.isEmpty()) {
return false;
}
Random rand = new Random();
int move = validMoves.get(rand.nextInt(validMoves.size()));
int nextRow = x + rowMoves[move];
int nextCol = y + colMoves[move]:
chessboard2[nextRow][nextCol] = moveNumb + 1;
return move(moveNum + 1, nextRow, nextCol, chessboard2);
}

There is a solution but it would require some refactoring:

• Create a ChessMove class that stores a row and a column move (integers)
• Add a ChessMove[] to store all possible moves that your knight can possibly do
• Refactor the move method:
  • Create an ArrayList<ChessMove> that stores all possible moves that your knight can do in its current position
  • Randomly select a move in this list using rand.nextInt(possibleMoves.size());

Here is the complete code:

package assignment3;
import java.lang.*;
import java.util.*;
public class Knight {
private int boardSize = 8;
private int[][] chessboard2 = new int[boardSize][boardSize];
private final ChessMove[] moves = {
new ChessMove(-1, 2), 
new ChessMove(-2, 1), 
new ChessMove(-2, -1), 
new ChessMove(-1, -2), 
new ChessMove(1, -2), 
new ChessMove(2, -1), 
new ChessMove(2, 1), 
new ChessMove(1, 2)
};
public Knight() {
initializeBoard();
}
public void initializeBoard() {
for (int i = 0; i < boardSize; i++)
Arrays.fill(chessboard2[i], Integer.MIN_VALUE); //setting array to negative value
}
public boolean move(int moveNum, int x, int y) {
//if moveNum == 64 all squares have been visited 
if (moveNum == 64) {
System.out.println("\ntrue board is 64\n");
return true;
}
ArrayList<ChessMove> possibleMoves = new ArrayList<ChessMove>();
for (ChessMove move : moves) {
int nextRow =  x + move.row;
int nextCol =  y + move.col;
//check if postion is valid and not visited yet
if (canMove(nextRow, nextCol) && chessboard2[nextRow][nextCol] == Integer.MIN_VALUE)
possibleMoves.add(move);
}
if (!possibleMoves.isEmpty()) {
Random rand = new Random();
// Move choice is done here
ChessMove chosenMove = possibleMoves.get(rand.nextInt(possibleMoves.size()));
int nextRow =  x + chosenMove.row;
int nextCol =  y + chosenMove.col;
//if move is valid knight moves
chessboard2[nextRow][nextCol] = moveNum + 1;
//make next move
move(moveNum + 1, nextRow, nextCol);
return true;
} else
return false;
}     
public boolean canMove(int x, int y) {
return (x >= 0 && x < boardSize && y >= 0 && y < boardSize);
}
public void print() {
for (int i = 0; i < boardSize; i++) {
for (int cell : chessboard2[i])
if (cell == Integer.MIN_VALUE)
System.out.print("*** ");
else
System.out.print(String.format("%3d", cell) + " ");
System.out.println();
}
}
public void solve() {
chessboard2[0][0] = 1;
if (move(1, 0, 0)) // if true, it will print chess board
print();
else //if false, there is no solution
System.out.print("no solution");
}
class ChessMove {
int row = 0, col = 0;
ChessMove(int r, int c) {
this.row = r;
this.col = c;
}
}
}
public class TesterMain {
public static void main(String[] args) {
Knight test = new Knight();
test.solve();
}
}

You can use an enum, let's call it Move, to represent every single move, and then make a list of these moves using Move.values().
Then you can shuffle the list with Collections.shuffle every time you want to move and take the first legal move.