Java中如何创建半满半空二维数组并添加新行填充？

我需要实现一个6列10行的棋盘，元素为随机数1、2、3。初始仅填充前5行，剩余5行留空。用户每次输入后，添加一行随机数替换空行，直到填满10行。

初始棋盘示例 #

3 1 1 2 2 2 
3 3 3 3 2 3 
1 1 1 3 3 2 
2 3 2 3 1 2 
3 3 1 2 2 2 

What column do you want to shoot at?

用户输入后的棋盘示例 #

3 1 1 2 2 2 
3 3 3 3 2 3 
1 1 1 3 3 2 
2 3 2 3 1 2 
3 3 1 2 2 2 
2 3 3 1 1 1

What column do you want to shoot at?

核心问题 #

• 如何创建半满半空的二维数组
• 如何在用户每次输入后，逐步用随机数行填充空行

现有代码 #

import java.util.Scanner;
public class Project {
    public static void main( String[] args) {
        Scanner scan = new Scanner(System.in);
        int [][] grid = createBoard(6, /*Number of colums*/ 5, /*Number of rows*/ 3 /*Bubble types in the board (1, 2 or 3)*/);
        printGrid( grid );
        System.out.println("What column do you want to shoot at?");
        shoot();
    }
    
      public static int[][] createBoard(int cols, int rows, int numBubbleTypes) {
        int[][] board = new int[rows][cols]; 
        for( int row = 0; row < rows;  row++ ) {
            for( int col = 0; col < cols; col++ ) {
                board[row][col] = (int)(Math.random() * (double)numBubbleTypes) + 1;
            }
        }
        return board;
    }
    
    public static void printGrid(int[][] grid) {
        for( int row = 0; row < grid.length; row++ ) {
            for( int col = 0; col < grid[row].length; col++ ) {
                System.out.print( grid[row][col] + " " ); 
            }
            System.out.println("");
        }
    }
    
  
    public static void fillBoard(int[] grid) {
        
    }
    
    public static void shoot() {
        Scanner scanShoot = new Scanner(System.in);
        String input = scanShoot.nextLine();
    }
    
    private static void clearConsole() {
        System.out.print('\u000C'); //Clear terminal
    }
    
}

解决方案 #

1. 创建半填充的二维数组 #

原createBoard只生成指定行数的数组，现在改成生成总10行的数组，仅填充前5行，剩余行用默认值0标记为空。

修改后的createBoard方法：

public static int[][] createBoard(int cols, int totalRows, int filledRows, int numBubbleTypes) {
    int[][] board = new int[totalRows][cols]; // 初始化总行数的数组
    // 填充前filledRows行的随机数
    for( int row = 0; row < filledRows;  row++ ) {
        for( int col = 0; col < cols; col++ ) {
            board[row][col] = (int)(Math.random() * numBubbleTypes) + 1;
        }
    }
    // 剩余行默认是0，代表空行
    return board;
}

在main方法中调用时，传入总行数10、初始填充行数5：

int [][] grid = createBoard(6, 10, 5, 3);

2. 修改打印方法，适配空行 #

原打印方法会输出空行的0，需要判断行是否全为0，是则打印空行，否则打印数字：

public static void printGrid(int[][] grid) {
    for( int row = 0; row < grid.length; row++ ) {
        boolean isEmptyRow = true;
        // 检查当前行是否全为0
        for( int val : grid[row] ) {
            if(val != 0) {
                isEmptyRow = false;
                break;
            }
        }
        if(isEmptyRow) {
            System.out.println(); // 空行直接换行
        } else {
            for( int val : grid[row] ) {
                System.out.print( val + " " ); 
            }
            System.out.println();
        }
    }
}

3. 实现逐步填充逻辑 #

在main方法中维护一个nextEmptyRow变量，记录下一个要填充的行索引。循环接收用户输入，每次输入后填充对应行，直到填满10行：

public static void main( String[] args) {
    Scanner scan = new Scanner(System.in);
    int totalRows = 10;
    int filledRowsInitially = 5;
    int [][] grid = createBoard(6, totalRows, filledRowsInitially, 3);
    int nextEmptyRow = filledRowsInitially; // 初始下一个空行是第5行（索引从0开始）

    while(nextEmptyRow < totalRows) {
        printGrid( grid );
        System.out.println("What column do you want to shoot at?");
        String input = scan.nextLine(); // 接收用户输入，无需处理内容，仅触发填充

        // 填充下一行
        fillNextRow(grid, nextEmptyRow, 3);
        nextEmptyRow++;

        // 可选：开启清屏，注释掉则保留历史输出
        // clearConsole();
    }

    // 填满后打印最终棋盘
    printGrid(grid);
    System.out.println("棋盘已填满！");
    scan.close();
}

实现填充单行的方法：

public static void fillNextRow(int[][] grid, int rowIndex, int numBubbleTypes) {
    int cols = grid[rowIndex].length;
    for( int col = 0; col < cols; col++ ) {
        grid[rowIndex][col] = (int)(Math.random() * numBubbleTypes) + 1;
    }
}

4. 整合后的完整代码 #

import java.util.Scanner;
public class Project {
    public static void main( String[] args) {
        Scanner scan = new Scanner(System.in);
        int totalRows = 10;
        int filledRowsInitially = 5;
        int [][] grid = createBoard(6, totalRows, filledRowsInitially, 3);
        int nextEmptyRow = filledRowsInitially;

        while(nextEmptyRow < totalRows) {
            printGrid( grid );
            System.out.println("What column do you want to shoot at?");
            String input = scan.nextLine();

            fillNextRow(grid, nextEmptyRow, 3);
            nextEmptyRow++;

            // clearConsole(); // 可选开启清屏
        }

        printGrid(grid);
        System.out.println("棋盘已填满！");
        scan.close();
    }
    
    public static int[][] createBoard(int cols, int totalRows, int filledRows, int numBubbleTypes) {
        int[][] board = new int[totalRows][cols];
        for( int row = 0; row < filledRows;  row++ ) {
            for( int col = 0; col < cols; col++ ) {
                board[row][col] = (int)(Math.random() * numBubbleTypes) + 1;
            }
        }
        return board;
    }
    
    public static void printGrid(int[][] grid) {
        for( int row = 0; row < grid.length; row++ ) {
            boolean isEmptyRow = true;
            for( int val : grid[row] ) {
                if(val != 0) {
                    isEmptyRow = false;
                    break;
                }
            }
            if(isEmptyRow) {
                System.out.println();
            } else {
                for( int val : grid[row] ) {
                    System.out.print( val + " " ); 
                }
                System.out.println();
            }
        }
    }
    
    public static void fillNextRow(int[][] grid, int rowIndex, int numBubbleTypes) {
        int cols = grid[rowIndex].length;
        for( int col = 0; col < cols; col++ ) {
            grid[rowIndex][col] = (int)(Math.random() * numBubbleTypes) + 1;
        }
    }
    
    private static void clearConsole() {
        System.out.print('\u000C'); // 清屏
    }
}

内容的提问来源于stack exchange，提问作者MazaPan616