以矩阵格式打印二维数组

Question

如何以矩阵框格式打印一个简单的 int[][] ，就像我们手写矩阵的格式一样。简单的循环运行显然不起作用。如果有帮助，我正在尝试在 linux ssh 终端中编译此代码。

for (int i = 0; i < rows; i++) {
    for (int j = 0; j < cols; j++) {
        System.out.println(matrix[i][j] + " ");
    }
    System.out.println();
}

Answer 1

要正确设置列中数字的格式，最好使用 printf。根据最大或最小数字的大小，您可能需要调整模式“%4d”。例如，要允许 Integer.MIN_VALUE 和 Integer.MAX_VALUE 之间的任何整数，请使用 "%12d"。

public void printMatrix(int[][] matrix) {
    for (int row = 0; row < matrix.length; row++) {
        for (int col = 0; col < matrix[row].length; col++) {
            System.out.printf("%4d", matrix[row][col]);
        }
        System.out.println();
    }
}

输出示例：

 36 913 888 908
732 626  61 237
  5   8  50 265
192 232 129 307

Answer 2

int[][] matrix = {
        {1, 2, 3},
        {4, 5, 6},
        {7, 8, 9},
        {10, 11, 12}
};

printMatrix(matrix);

public void printMatrix(int[][] m) {
    try {
        int rows = m.length;
        int columns = m[0].length;
        String str = "|\t";

        for (int i = 0; i < rows; i++) {
            for (int j = 0; j < columns; j++) {
                str += m[i][j] + "\t";
            }
            System.out.println(str + "|");
            str = "|\t";
        }
    } catch (Exception e) {
        System.out.println("Matrix is empty!!");
    }
}

输出：

|   1   2   3   |
|   4   5   6   |
|   7   8   9   |
|   10  11  12  |

Answer 3

在Java 8中：

import java.util.Arrays;

public class MatrixPrinter {
  public static void main(String[] args) {
    final int[][] matrix = new int[4][4];
    printMatrix(matrix);
  }

  public static void printMatrix(int[][] matrix) {
    Arrays.stream(matrix).forEach((row) -> {
      System.out.print("[");
      Arrays.stream(row).forEach((el) -> System.out.print(" " + el + " "));
      System.out.println("]");
    });
  }
}

这会产生：

[ 0  0  0  0 ]
[ 0  0  0  0 ]
[ 0  0  0  0 ]
[ 0  0  0  0 ]

但是既然我们在这里，为什么不让行布局可定制呢？

我们所需要做的就是将 lamba 传递给 matrixPrinter 方法：

import java.util.Arrays;
import java.util.function.Consumer;

public class MatrixPrinter {
  public static void main(String[] args) {
    final int[][] matrix = new int[3][3];

    Consumer<int[]> noDelimiter = (row) -> {
      Arrays.stream(row).forEach((el) -> System.out.print(" " + el + " "));
      System.out.println();
    };

    Consumer<int[]> pipeDelimiter = (row) -> {
      Arrays.stream(row).forEach((el) -> System.out.print("| " + el + " "));
      System.out.println("|");
    };

    Consumer<int[]> likeAList = (row) -> {
      System.out.print("[");
      Arrays.stream(row).forEach((el) -> System.out.print(" " + el + " "));
      System.out.println("]");
    };

    printMatrix(matrix, noDelimiter);
    System.out.println();
    printMatrix(matrix, pipeDelimiter);
    System.out.println();
    printMatrix(matrix, likeAList);
  }

  public static void printMatrix(int[][] matrix, Consumer<int[]> rowPrinter) {
    Arrays.stream(matrix).forEach((row) -> rowPrinter.accept(row));
  }
}

结果如下：

 0  0  0 
 0  0  0 
 0  0  0 

| 0 | 0 | 0 |
| 0 | 0 | 0 |
| 0 | 0 | 0 |

[ 0  0  0 ]
[ 0  0  0 ]
[ 0  0  0 ]

Answer 4

int[][] matrix = {
        {1, 2, 3},
        {4, 5, 6},
        {7, 8, 9}
};
//use foreach loop as below to avoid IndexOutOfBoundException
//need to check matrix != null if implements as a method
//for each row in the matrix
for (int[] row : matrix) {
    //for each number in the row
    for (int j : row) {
        System.out.print(j + " ");
    }
    System.out.println("");
}

Answer 5

public static void printMatrix(double[][] matrix) {
    for (double[] row : matrix) {
        for (double element : row) {
            System.out.printf("%5.1f", element);
        }
        System.out.println();
    }
}

---

函数调用

printMatrix(new double[][]{2,0,0},{0,2,0},{0,0,3}});

输出

  2.0  0.0  0.0
  0.0  2.0  0.0
  0.0  0.0  3.0

---

控制台中的

Answer 6

自 Java 8 起：

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

Arrays.stream(matrix).map(Arrays::toString).forEach(System.out::println);

输出：

[1, 2, 3]
[4, 5, 6]
[7, 8, 9]

Answer 7

这是我使用 StringBuilder 数组显示 2D 整数数组的有效方法。

public static void printMatrix(int[][] arr) {
    if (null == arr || arr.length == 0) {
        // empty or null matrix
        return;
    }

    int idx = -1;
    StringBuilder[] sbArr = new StringBuilder[arr.length];

    for (int[] row : arr) {
        sbArr[++idx] = new StringBuilder("(\t");

        for (int elem : row) {
            sbArr[idx].append(elem + "\t");
        }

        sbArr[idx].append(")");
    }

    for (int i = 0; i < sbArr.length; i++) {
        System.out.println(sbArr[i]);
    }
    System.out.println("\nDONE\n");
}

输出：

(   1   2   3   )
(   4   5   6   )
(   7   8   9   )
(   10  11  12  )

DONE

Answer 8

public class Matrix {
    public static void main(String[] args) {
        double Matrix[][] = {
                {0*1, 0*2, 0*3, 0*4},
                {0*1, 1*1, 2*1, 3*1},
                {0*2, 1*2, 2*2, 3*2},
                {0*3, 1*3, 2*3, 3*3}};

        int i, j;
        for (i = 0; i < 4; i++) {
            for (j = 0; j < 4; j++)
                System.out.print(Matrix[i][j] + " ");
            System.out.println();
        }
    }
}

输出：

0.0 0.0 0.0 0.0 
0.0 1.0 2.0 3.0 
0.0 2.0 4.0 6.0 
0.0 3.0 6.0 9.0 

Answer 9

我更喜欢在 Java 中使用增强循环

，因为我们的 ar 是一个数组的数组 [2D]。因此，当您对其进行迭代时，您将首先获得一个数组，然后您可以迭代该数组以获取各个元素。

public static void main(String[] args) {
    int[][] ar = {
            {12, 33, 23},
            {34, 56, 75},
            {14, 76, 89},
            {45, 87, 20}};

    for (int[] num : ar) {
        for (int ele : num) {
            System.out.print(" " + ele);
        }
        System.out.println(" ");
    }
}

输出：

 12 33 23 
 34 56 75 
 14 76 89 
 45 87 20 

Answer 10

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

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();
}

生产：

1 2 3
4 5 6
7 8 9