打印3D阵列

Question

I am trying to print a 3D Array. This is my code:

    public static void print(int [][][] array)
{
    for (int i=0; i<array.length; i++ )
    {
        for (int x=0; x<array[i].length;x++)
        {
            System.out.println();
            System.out.print("row "+ x);
            for (int j=0; j<array[i][x].length;j++)
            {
                    System.out.print (array[i][x][j]+ " ");
            }
        }
    }

Is there something am I doing wrong? Every time I call

 ThreeDRay.print(d3);

I get this error:

Exception in thread "main" java.lang.NullPointerException at ThreeDRay.print(ThreeDRay.java:13) at ThreeDRayRunner.main(ThreeDRayRunner.java:54)

The rest of the code is this:

    public static void main( String args[] )
{
Scanner keyboard = new Scanner(in);

    out.print("How many matrices do you wish to enter? :: ");
    int matCnt = keyboard.nextInt();

    //instantiate a ThreeDRay

    int[][][] d3= new int [matCnt][][];


    for (int x=0; x < d3.length ;++x){
          d3[x] = new int[0][0];

    for(int i = 0; i < matCnt; i++)
    {
        out.print("What is the size of matrix " + i + " : ");
        int size = keyboard.nextInt();

        int[][] mat = new int[size][size];
        out.println();


        for(int r=0; r<mat.length; r++)
        {
            for(int c=0; c<mat[r].length; c++)
            {
                out.print("Enter a value for spot " + r + " - " + c + " :: ");
               mat[r][c]=keyboard.nextInt();
            }
        }



    if (i==0 && i<matCnt)
    {
    for (int l=0; l<=matCnt; l++){
          out.println("\nThreeDRay before setting mat at spot "+l);



    }
    }


       ThreeDRay.print(d3);


       d3[i] = mat;


        out.println("\nThreeDRay after setting mat at spot "+i);

           ThreeDRay.print(d3);

I have to show how I filled the matrices

 //user inputs values for first matrix 

Before adding:

Array [0] =

Array [1] =

Array [2] =

//add user inputs

After adding:

Array [0] = row 0 = [...]

  row 1 = [...] ... depending on user given size of the first matrix Array[1] = Array[2] = 

//ask for inputs for second matrix

Before Adding

Array [0] = row 0 = [...]

  row 1 = [...] ... depending on user given size of the first matrix Array[1] = Array[2] = 

After adding

Array [0] = row 0 = [...]

  row 1 = [...] ... depending on user given size of the first matrix 

Array[1] = row 0 = [...]

  row 1 = [...] ... depending on user given size of the first matrix 

Array[2] =

Answer 1

You need to close the curly brace in this for loop:

    for (int x = 0; x < d3.length; ++x) {
        d3[x] = new int[0][0];
    }

Without the closing brace, your program continues into the next for loop after having initialized only one element of d3 while remaining elements are still null, which gives a NullPointerException when you try to print the entire d3 underway.