这是一个使用JTable的程序实例。在这程序中，Table的其中一列是ComboBox。每次执行操作使ComboBox的值改变后，都会捕获系统时间。现在的问题是每次进行操作，监听器都会执行两次；而且ComboBox不能连续两次选一样的值，否则监听器不工作。-This is an instance of the JTable. In this program, the Table, which a ComboBox. Will capture each execution of the operation so that the value of the ComboBox to change the system time. The question now is each operation, the listener will be executed twice　ComboBox not twice to choose the same value, or the listener does not work.