[英]Printing 3D Arrays
我正在尝试打印3D阵列。 这是我的代码:
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]+ " ");
}
}
}
我做错什么了吗? 每次我打电话
ThreeDRay.print(d3);
我收到此错误:
在ThreeDRayRunner.main(ThreeDRayRunner.java:54)的ThreeDRay.print(ThreeDRay.java:13)处的线程“ main”中的java.lang.NullPointerException异常
其余代码如下:
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);
我必须证明我如何填充矩阵
//user inputs values for first matrix
在添加之前:
数组[0] =
数组[1] =
数组[2] =
//添加用户输入
添加后:
数组[0] =行0 = [...]
row 1 = [...] ... depending on user given size of the first matrix Array[1] = Array[2] =
//询问第二个矩阵的输入
在添加之前
数组[0] =行0 = [...]
row 1 = [...] ... depending on user given size of the first matrix Array[1] = Array[2] =
添加后
数组[0] =行0 = [...]
row 1 = [...] ... depending on user given size of the first matrix
数组[1] =行0 = [...]
row 1 = [...] ... depending on user given size of the first matrix
数组[2] =
您需要在此for循环中关闭花括号:
for (int x = 0; x < d3.length; ++x) {
d3[x] = new int[0][0];
}
如果没有大括号,您的程序将仅初始化d3
一个元素,而其余元素仍为null之后,将继续进入下一个for循环,当您尝试打印正在执行的整个d3
时,将给出NullPointerException
。
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