面向對象三大特性之一是封裝,類中的域(變量),盡量使用private,如果真要通路,可以提供get和set,以避免破壞封裝性。
但是,如果get通路器中傳回的是引用類型對象的話,那也有可能會被外界所修改,進而破壞封裝性。如:
public class Employee {
private Date hireDay;
public Date getHireDay(){
return this.hireDay;
}
private String name;
public Employee(String name){
this.name = name;
}
public boolean equals(Employee other){
return name.equalsIgnoreCase(other.name);
}
}
Employee zhang3 = new Employee("zhang3");
Date d = zhang3.getHireDay();
d.setTime(d.getTime() - 10000000);