说明：  编写一个Swing应用程序，模拟交通红绿灯。程序允许用户选择3种灯的一种：红、黄、绿。当一个按钮被选中时，相就的灯就被打开，一次只能打开一个灯。程序启动时，没有灯打开。
(The preparation of a Swing application, simulation of traffic lights. Procedures permit the user to choose one of three kinds of lights: red, yellow and green. When a button is selected, the phase of the lights on was open, one can open a lamp. Proceedings did not turn on the light.)