Java™ How To Program (Early Objects), Tenth Edition

Java’s Coordinate System

To draw in Java, you must understand Java’s coordinate system (Fig. 4.17), a scheme for identifying points on the screen. By default, the upper-left corner of a GUI component has the coordinates (0, 0). A coordinate pair is composed of an x-coordinate (the horizontal coordinate) and a y-coordinate (the vertical coordinate). The x-coordinate is the horizontal location moving from left to right. The y-coordinate is the vertical location moving from top to bottom. The x-axis describes every horizontal coordinate, and the y-axis every vertical coordinate. Coordinates indicate where graphics should be displayed on a screen. Coordinate units are measured in pixels. The term pixel stands for “picture element.” A pixel is a ...