英文:
Trying to count the amount of objects created
问题
我在创建 x 个对象之前和之后，两个计数器都一直得到 0。
class Thing {
private static int count = 0;
public Thing() {
count++;
}
public static int getCount(){
return count;
}
}
public class getCounter {
public static void main(String[] args) {
int counter = Thing.getCount();
System.out.println("已创建的对象数：" + counter);
Thing thing1 = new Thing();
Thing thing2 = new Thing();
System.out.println("已创建的对象数：" + Thing.getCount());
}
}
英文:
I keep getting 0 for both counters before and after creating x amount of objects.
class Thing {
private static int count = 0;
public Thing() {
count++;
}
public static int getCount(){
return count;
}
}
public class getCounter {
public static void main(String[] args) {
int counter = Thing.getCount();
System.out.println("Objects created: " + counter);
Thing thing1 = new Thing();
Thing thing2 = new Thing();
System.out.println("Objects created: " + counter);
}
}
答案1
得分: 4
你需要再次调用getCount()以获取更新后的计数。如果你将它缓存在一个变量中，你将始终获得相同的值。
public static void main(String[] args) {
System.out.println("创建的对象数：" + Thing.getCount());
Thing thing1 = new Thing();
Thing thing2 = new Thing();
System.out.println("创建的对象数：" + Thing.getCount());
}
英文:
You need to call getCount() again to get an updated count. If you cache it in a variable you'll always have the same value.
public static void main(String[] args) {
System.out.println("Objects created: " + Thing.getCount());
Thing thing1 = new Thing();
Thing thing2 = new Thing();
System.out.println("Objects created: " + Thing.getCount());
}
答案2
得分: 0
只是在John的正确答案上补充并解释 - 为什么他的答案是正确的：
将值赋给变量，就是在执行的特定时间将该值存储在该变量中。
例如：
int x = Math.sqrt(25);
意味着将由Math.sqrt(25)返回的值（即5）存储到变量x中。
你将从getCount()获得的值存储在局部变量counter中，但你从未更新它，而且无论你创建了多少个对象，如果counter变量保持不变，它的值始终为0。
在构造函数更新类成员counter两次之后，你可能希望再次调用getCount()以检索最新的值。
英文:
Just to add on John's correct answer and explain - why his answer is correct:
Assignment of the value to the variable, is storing that value in that variable at a particular time of execution.
For example:
int x = Math.sqrt(25);
Means to store the value returned by Math.sqrt(25) (which is 5), into variable x.
You store the value returned from getCount() in the local variable counter, but you never update it, and disregarding of how many objects you'll create, if counter variable remains like it is, it will always have the same value 0.
After your constructor updates the class member counter twice, you might want to call getCount() again to retrieve the up to date value.
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