1)　　设计表示学生的类Student，包括域“学号”、“班级”、“性别”、“年龄”等，方法“获得学号”、“获得性别”、“获得姓名”、“获得年龄”、“修改年龄”等。

另加一个方法public String toString（）把Student类对象的所有域信息组合成一个字符串。

-1) indicates that the student design class Student, including domain " study" , " class" , " sex" , " age"　and other methods " to get Student ID" , " get sex" , " get name" , " age of acquisition"　" Change Age"　and so on. Plus a method public String toString () to combine all domain information Student class object into a string.