创建一个四则运算的java类，并创建一个继承该类的一个子类，要求覆盖父类中求和的方法，并分别调用子父类中求和的方法。

包含相关代码和运行结果。-Create a java computing four categories, and create a succession of such a sub-category, the coverage demanded by the parent class summation method, and the respective sub-call parent class method in the summation. Contains the relevant code and operating results.