英文:
In Java, what would be an easy way to number objects?
问题
第一个创建的对象在创建时知道它是"对象 1"。
第二个创建的对象在创建时知道它是"对象 2"，依此类推。
英文:
e.g
the first object created knows that it is "object 1" when created.
the second object created knows that it is "object 2" when created etc.
答案1
得分: 5
这确实取决于使用情况，以下对于大多数情况可能不是一个好的解决方案。
但总的来说，你可以使用一个静态成员变量并在构造函数中进行递增：
public class Example {
private static int counter = 0;
private final int id;
public Example() {
id = counter++;
}
}
需要注意的是，这也会在应用程序多线程时导致同步问题：一般来说，并发更新这个静态变量是不安全的。要修复这个问题，需要使用synchronized方法来递增变量，或将其声明为AtomicInteger。
英文:
It really depends on the use-case, and the following is probably not a good solution for most of them.
But in general you can use a static member variable and increment it in the constructur:
public class Example {
private static int counter = 0;
private final int id;
public Example() {
id = counter++;
}
}
Note that this also causes synchronisation problems once your application is multi-threaded: in general it is not safe to update this static variable concurrently. To fix this would require either using a synchronized method to increment the variable, or declaring it as an AtomicInteger.
答案2
得分: 0
你可以保留一个内部静态计数器（nextId）作为序列生成器，并使用实例字段来保存每个对象的值：
public class OrderedObject {
private static int nextId = 1;
private int id = nextId++;
public int getOrder() {
return id;
}
public String toString() {
return "OrderedObject-" + id;
}
public static void main(String args[]) {
System.out.println(new OrderedObject());
System.out.println(new OrderedObject());
System.out.println(new OrderedObject());
}
}
英文:
You can keep an internal static counter(nextId) as asequence generator and an instance field to keep the value per object:
public class OrderedObject {
private static int nextId=1;
private int id=nextId++;
public int getOrder() {
return id;
}
public String toString()
{
return "OrderedObject-"+id;
}
public static void main(String args[])
{
System.out.println(new OrderedObject());
System.out.println(new OrderedObject());
System.out.println(new OrderedObject());
}
}
通过集体智慧和协作来改善编程学习和解决问题的方式。致力于成为全球开发者共同参与的知识库，让每个人都能够通过互相帮助和分享经验来进步。
评论