isa”关系 public class Employee i private String name 个最初的模型派生出多个 private Date hireDate;,理 Manager。显然,一名 private Date datenfRirth boolu A且≠ private Str/ public class Manager private int private String name private Date hireDate private Date dateOfBirth private string jobTitle private int grade; private string department private Employee L subordinates“is a ”关系 ▪ 一般与特殊的关系 ▪ 雇员Employee，从这个最初的模型派生出多个 具体化的版本，如经理Manager。显然，一名 Manager首先是一位Employee，他具有 Employee的一般特性。除此之外，Manager还 有Employee所不具有的额外特性 public class Employee { private String name; private Date hireDate; private Date dateOfBirth; private String jobTitle; private int grade; ... public class Manager { private String name; private Date hireDate; private Date dateOfBirth; private String jobTitle; private int grade; private String department; private Employee [] subordinates; ... }