如何在 Java 中漂亮地打印 3D 数组

Question

I have a three-dimensional int array and would like to pretty-print it in this format:

[n,n,n] [n,n,n] [n,n,n]
[n,n,n] [n,n,n] [n,n,n]
[n,n,n] [n,n,n] [n,n,n]

[n,n,n] [n,n,n] [n,n,n]
[n,n,n] [n,n,n] [n,n,n]
[n,n,n] [n,n,n] [n,n,n]

[n,n,n] [n,n,n] [n,n,n]
[n,n,n] [n,n,n] [n,n,n]
[n,n,n] [n,n,n] [n,n,n]

I tried using the code below but it didn't print it right because the second and third columns have to be appended to the same line as the first column:

int[][][] hardestOne = {
    {{8, 0, 0, 0, 0, 3, 0, 7, 0}, {0, 0, 0, 6, 0, 0, 0, 9, 0}, {0, 0, 0, 0, 0, 0, 2, 0, 0}},
    {{0, 5, 0, 0, 0, 0, 0, 0, 0}, {0, 0, 7, 0, 4, 5, 1, 0, 0}, {0, 0, 0, 7, 0, 0, 0, 3, 0}},
    {{0, 0, 1, 0, 0, 8, 0, 9, 0}, {0, 0, 0, 5, 0, 0, 0, 0, 0}, {0, 6, 8, 0, 1, 0, 4, 0, 0}}
};

public String toString() {
    String s = "";

    for (int i = 0; i < table.length; i++) {
        for (int j = 0; j < table[i].length; j++) {
            for (int k = 0; k < table[i][j].length; k++) {
                if (k == 2 || k == 5) {
                    s += table[i][j][k] + "\n";
                } else {
                    s += table[i][j][k] + "";
                }
            }
            s += "\n\n";
        }
        s += "\n";
    }

    return s;
}

UPDATE: I changed the example array to be more readable.

UPDATE 2: User @samurott gave a really good answer but there is this problem:

Consider these three lines which represent the first block in my array

{{8, 0, 0}, {0, 0, 3}, {0, 7, 0}},
{{0, 0, 0}, {6, 0, 0}, {0, 9, 0}},
{{0, 0, 0}, {0, 0, 0}, {2, 0, 0}}

Looking at those lines above the printing should look like this

[8,0,0] [0,0,0] [0,0,0]
[0,0,3] [6,0,0] [0,0,0]
[0,7,0] [0,9,0] [2,0,0]

But when I print it using his code it looks like this

[8,0,0] [0,0,3] [0,7,0]
[0,0,0] [6,0,0] [0,9,0]
[0,0,0] [0,0,0] [2,0,0]

You see I could change all the positions of the array but it's gonna get more and more confusing later on.

SOLUTION: See the solution below made by user @Alex R

Answer 1

Here would be a reusable solution for 3x3 matrices. This only works if the array contains numbers from 0 to 9. Additional formatting is needed if you want to support other integers as well.

public final class TableFormatter {
private static final int[][][] TABLE = {
        {{8, 0, 0, 0, 0, 3, 0, 7, 0}, {0, 0, 0, 6, 0, 0, 0, 9, 0}, {0, 0, 0, 0, 0, 0, 2, 0, 0}},
        {{0, 5, 0, 0, 0, 0, 0, 0, 0}, {0, 0, 7, 0, 4, 5, 1, 0, 0}, {0, 0, 0, 7, 0, 0, 0, 3, 0}},
        {{0, 0, 1, 0, 0, 8, 0, 9, 0}, {0, 0, 0, 5, 0, 0, 0, 0, 0}, {0, 6, 8, 0, 1, 0, 4, 0, 0}}
};

public static void main(String[] args) {
    TableFormatter formatter = new TableFormatter(TABLE);
    System.out.println(formatter.toString());
}

private final int[][][] array3d;

public TableFormatter(int[][][] array3d) {
    this.array3d = array3d;
}

@Override
public String toString() {
    StringBuilder builder = new StringBuilder();
    for (int[][] array2d : array3d) {
        append2dArray(builder, array2d);
        builder.append('\n');
    }
    return builder.toString();
}

private void append2dArray(StringBuilder builder3d, int[][] array2d) {
    for (int i = 0; i < 3; i++) {
        for (int j = 0; j < 3; j++) {
            StringBuilder builder2d = new StringBuilder("[");
            for (int k = 0; k < 3; k++) {
                builder2d.append(array2d[j][(i * 3) + k]).append(',');
            }
            builder2d.deleteCharAt(builder2d.length() - 1).append("]\t");
            builder3d.append(builder2d);
        }
        builder3d.append('\n');
    }
}
}

Output:

[8,0,0] [0,0,0] [0,0,0] 
[0,0,3] [6,0,0] [0,0,0] 
[0,7,0] [0,9,0] [2,0,0] 

[0,5,0] [0,0,7] [0,0,0] 
[0,0,0] [0,4,5] [7,0,0] 
[0,0,0] [1,0,0] [0,3,0] 

[0,0,1] [0,0,0] [0,6,8] 
[0,0,8] [5,0,0] [0,1,0] 
[0,9,0] [0,0,0] [4,0,0] 

If you want support for general matrices, you would have to pass the dimension as an argument to the constructor and update the loop variables so that they use that dimension.

Answer 2

I believe what you're trying to print is a 4-dimensional array, not a 3-dimensional one, as you have 4 layers of grouping. However, here's the modified pretty-print loop:

for (int i = 0; i < table.length; i++){
    for (int j = 0; j < table[i].length; j++){
        for (int k = 0; k < table[i][j].length; k++){
            s += "[";
            for (int l = 0; l < table[i][j][k].length; l++){
                s += table[i][j][k][l];
                if (l != table[i][j][k].length - 1){
                    s += ",";
                }
            }
            s += "]";
            if (k != table[i][j].length - 1){
                s += " ";
            }
        }
        s += "\n";
    }
    s += "\n";
}

This is the modified value table I'm using:

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

Answer 3

I made very minor changes to your code. The problem is that k loops over your inner data and you put a newline in several places. I don't think that's what you wanted. You then add more newlines after each loop of k. I removed the extra newlines and then fiddled slightly with making it pretty.

public class X {

    int[][][] table = {
        {{1, 2, 3, 4, 5, 6, 7, 8, 9}, {11, 12, 13, 14, 15, 16, 17, 18, 19}, {21, 22, 23, 24, 25, 26, 27, 28, 29}},
        {{101, 102, 103, 104, 105, 106, 107, 108, 109}, {111, 112, 113, 114, 115, 116, 117, 118, 119}, {121, 122, 123, 124, 125, 126, 127, 128, 129}},
        {{201, 202, 203, 204, 205, 206, 207, 208, 209}, {211, 212, 213, 214, 215, 216, 217, 218, 219}, {221, 222, 223, 224, 225, 226, 227, 228, 229}},
    };

    public String toString() {
        String s = "";

        for (int i = 0; i < table.length; i++) {
            for (int j = 0; j < table[i].length; j++) {
                s += (j == 0) ? "[" : " [";


                for (int k = 0; k < table[i][j].length; k++) {
                    if (k > 0) {
                        s += ", ";
                    }
                    s += table[i][j][k];
                }
                s += "]";
            }
            s += "\n";
        }

        return s;
    }

    public static void main(String[] args) {
        X foo = new X();
        System.out.println(foo.toString() );
    }
}

$ javac X.java && java X
[1, 2, 3, 4, 5, 6, 7, 8, 9] [11, 12, 13, 14, 15, 16, 17, 18, 19] [21, 22, 23, 24, 25, 26, 27, 28, 29]
[101, 102, 103, 104, 105, 106, 107, 108, 109] [111, 112, 113, 114, 115, 116, 117, 118, 119] [121, 122, 123, 124, 125, 126, 127, 128, 129]
[201, 202, 203, 204, 205, 206, 207, 208, 209] [211, 212, 213, 214, 215, 216, 217, 218, 219] [221, 222, 223, 224, 225, 226, 227, 228, 229]