Add A New Jbutton For Every Empty Cell In Array

im trying to make a gui im trying to add a new jbutton for every empty cell in the array, and for some reason its giving me array index out of bounds error, this is what i have, im trying to to do it in an 80 by 80 array.

public JButton[][] buttons = new JButton[80][80];

public void addButtons(){
for(int i=0;i<buttons.length;i++){
for(int j=0;i<buttons[i].length;j++){
buttons[i][j]= new JButton();
}
}

}