Question

public class Office {
private char building;
private int floor;
private int roomnumber;}

public class Employee {
private String firstname;
private String lastname;
private String mail;
private String phone;
private Office office;}

我正在使用Java创建一个Office，并且每个员工只能限制一个办公室，这意味着Office的每个实例只能由一个Employee使用。 Office由Office Class制作，包含在Employee Class中。有没有人对如何做到这一点有任何建议？

Answer 1

如果您的意思是只想创建一个Office对象，则需要执行以下操作：您可以拥有boolean类型的静态类变量，一旦第一个实例生成，您将更改为true。在创建一个新实例时，您将检查此布尔值是否为真，如果是，则可以抛出异常等。
示例：

private static boolean hasBeenInstanciated = false;

public Constructor(){
    if(hasBeenInstanciated){
        throw new IllegalStateException("This class has already been instanciated once!");
    }else hasBeenInstanciated = true;
//The rest of your constructor code goes here.
}

Answer 2

这是一种方法：

创建Set<String>并开始将building_floor_roomnumber作为密钥放置。
在初始化Office之前，检查“设置”中是否已存在building_floor_roomnumber。

这是一个展示它的小片段：

public static void main (String[] args) 
{
    /* You can also make it global; depending on your needs */
    Set<String> office = new HashSet<>();
    String key = "A12-London_F6_R121";

    if(office.contains(key)) {
        System.out.println("Already Taken!");
    } else {
        office.add(key);

        /* Create New Office Object & Initialize it */
        Office off = new Office();
        off.setBuilding("A12-London");
        off.setFloor("F6");
        off.setRoom("R121");

        /* Set it back to Employee Object */
        /* I'm assuming you have some Employee Object named emp */
        emp.setOffice(off);

        System.out.println("Added Successfully!");
    }
}

限制构造函数

2 个答案: