"this.elements" is null error

Question

Hello everyone. I do't know what to do in this situation tbh. I can not find where is the mistake. Can you help me ?

public class cMatrix {
private long [][] elements;
private int row;
private int col;

/**
* @param args the command line arguments
*/
public static void main(String[] args) {
// TODO code application logic here
cMatrix m1 = new cMatrix();
m1.AssignRandom();
m1.printMatrix();

}

public cMatrix(){
row = 10;
col = 10;
for (int i = 0; i < row; i++){
for (int j = 0; j < col; j++){

}
}
}

public cMatrix(int row, int col){
this.row = row;
this.col = col;

}

public void AssignRandom(){

Random randomNum = new Random();
for (int i = 0; i < row; i++){
for (int j = 0; j < col; j++){
long s;
s = randomNum.nextLong(10000);

}
}
}

public void printMatrix(){

for (int i = 0; i < row; i++){
for (int j = 0; j < col; j++){
System.out.print(elements[i][j] + " ");
}
System.out.println(" ");
}
}

Answer 1

u didnt assign values to the elements

Answer 2

Can you tell me how can I do it ? 【ＡＣＥ】