What is happening right now?

JButton walls = new JButton; for(int i = 0;i<13;i++) { for(int j = 0; j<16; j++) { JButton wall = new JButton (); wall.setBackground(Color.white); wall.setBorderPainted(false); wall.setIcon(new ImageIcon("C:\\Users\\dell\\Downloads\\images (2)\\images\\grey.jpg")); walls=wall; if(j == 7 || j == 8) { wall.setIcon(new ImageIcon("C:\\Users\\dell\\Downloads\\images (2)\\images\\wall.jpg")); walls=wall; } panel_1.add(walls); }

Immediately after this, you will need to check for a null reference: <Code Omitted> Line 4 must not be executed without first checking that the list is not empty. Also, the list object must be type cast to Actor before it can be assigned to the reference variable: <Code Omitted> Similar to the first code set. Similar to the second code set. ****************************************************** Once you have the actor referenced, you will need to type cast it as a Crab object before you can access the crabHealth field: <Code Omitted>