I'm writing a program using JGrasp, where tile is a class. The Following code compiles:
tile ext = new tile();
ext.assignValues(0);
g.setColor(ext.color);
g.fillRect(10+20, 35+20, 20, 20);
But the following does not:
tile[][] ext = new tile[1][1];
ext[0][0].assignValues(0);
g.setColor(ext[0][0].color);
g.fillRect(10+20, 35+20, 20, 20);
Am I initializing the 2D array wrong, or am I misunderstanding how arrays work.
ext[0][0] not initialized as tile[][] ext = new tile[1][1]; is Array of instances of tile (Object In general term) but you have to initialize every object stored at array index before using those objects as default value is null for every element here.
tile ext[0][0]= new tile(); //Have to initialize it first
//And than use it in your code
As I think you won't get anny issue during compilation but it will throw NullPointerException while you execute your code which is trying to manipulate null value.
You have initialized the array ext[][], but you have not initialized the tile in position [0][0]. Therefore it is empty, and trying to call a method would be like accessing a method of a null value.
tile[][] ext = new tile[1][1];
ext[0][0] = new tile();
ext[0][0].assignValues(0);
g.setColor(ext[0][0].color);
g.fillRect(10+20, 35+20, 20, 20);
