JPanel

Although you could draw directly on the JFrame, it is more convenient to draw on a JPanel. Put the JPanel in the JFrame and draw on the JPanel. Think of a JPanel as a sheet of paper that represents the drawing surface of the frame. Think of the JFrame as a picture frame around the sheet of paper. A JPanel is a container object that can be drawn on and can contain other AWT components.

A JPanel is a rectangle width pixels across and height pixels in height. A location in the rectangle is described as (X, Y) where X and Y are integers. The (0, 0) location is at the top left.

Columns are numbered 0 to width-1 starting at the left. Rows are numbered 0 to height-1 starting at the top.