编写一个Ellipsoid类，用于椭球体的表示，其中定义三个私有变量表示一个椭球体的长半轴a短半轴b和扁率apha(Write a Ellipsoid class, used to represent the ellipsoid, which defined three private variables represents an ellipsoid semimajor axis semiminor axis B and a of APHA)