问题描述：本实验综合体现面向对象程序设计技术。此实验需应用面向对象程序设计课程中的“封装和继承”的基本原理，本课程中“类、对象和接口”的基本概念、以及“Java的事件处理机制”、“图形用户界面设计”技术，自己构思，编写一个具有如下布局的小应用程序，要求当在上面的文本区中输入若干数时，下面的文本框同时对输入的数进行求和运算并求出平均数。即随着输入的变化，文本框不断更新求和及平均值。

文档中有实验要求和详细的源代码.-Problem Descr iption: In this experiment, the integrated embodiment of object-oriented programming design techniques. This experiment required the application of object-oriented programming courses in the　Packaging and inheritance,　the basic principles, the courses　category, objects and interfaces,　the basic concept, as well as the　Java s event handling mechanism,　 graphical user interface design　technology, its own ideas, have the following layout of the preparation of a small application, and request the text in the above areas, type the number of a few hours, the following text box at the same time the number of input and calculated the average sum computing. With the input that changes in the text box and the average sum of continuously updated. Document in detail the experimental requirements and the source code.