英文:
java class "a" run method when class "a" created
问题
如何在创建类a的对象时运行"print()"方法？我想在行"a obj = new a();"之后立即运行"print()"方法。
我的意思是，只调用类，而不是方法。这样它将在调用后立即运行。
class a {
public static void print() {
System.out.println("Hey!");
}
}
public class MyClass {
public static void main(String[] args) {
a obj = new a();
a.print(); // 我想在这之后立即运行print()方法
}
}
英文:
how to run "print()" method when class a created as object? I want to run "print()" method right after the line "a obj = new a();"
I mean, just call the class, not the method. That it will operate immediately after the calling
class a {
public static void print() {
System.out.println("Hey!");
}
}
public class MyClass {
public static void main(String[] args) {
a obj = new a(); // I want to run print() method right after it
}
}
答案1
得分: 1
我猜这可能是某种奇怪的Java难题（为什么你不直接在构造函数中放置print()呢？），你可以将它放在初始化程序中：
class a {
{ print(); }
public static void print() {
System.out.println("Hey!");
}
}
这将完成任务。但这是一个非常愚蠢的想法 - 在类文件级别上，无论你是这样做还是将print()语句放在构造函数中，都是一样的。我们只是在吹毛求疵语言特性。
也许退一步。你遇到了一些未知的问题。你想：我知道！我只需要以某种方式使得构造该类的对象会导致print方法运行，但又不用在构造函数中调用print！哦，但是，我怎么做呢 - 最好问问Stack Overflow。
那个想法是错误的。所以陈述一下未知的问题，而不是问一个关于错误“解决方案”的问题。
注：你还可以创建静态初始化程序，例如：
class a {
static { print(); }
public static void print() {
System.out.println("Hey!");
}
}
现在print()实际上会在那个构造函数之前运行。它也只会运行一次，就是静态初始化程序的目的：它们在你对那个a类稍微有点怪异的操作时就开始运行（无论你对它做了什么），在运行一次之后就不会再运行。
你的问题相当不清楚，所以我只是随意猜测。
英文:
I guess if this is some sort of weird java puzzler (why the heck wouldn't you just put print() in the constructor?), you can put it in an initializer:
class a {
{ print(); }
public static void print() {
System.out.println("Hey!");
}
}
will get the job done. But this is a very silly idea - at the class file level it's all the same thing, whether you do this or put the print() statement in a constructor. We're just nitpicking on language features at this point.
Perhaps take a step back. You had some unknown problem. You thought: I know! I'll just somehow make construction of objects of this class cause the print method to run, but without putting a call to print in the constructor! Oh, but, how do I do that - better ask SO.
That was the wrong thought. So state the unknown problem instead of a question about a bad 'solution'.
NB: You can also make static initializers, e.g:
class a {
static { print(); }
public static void print() {
System.out.println("Hey!");
}
}
And now print() will in fact run before that constructor. It'll also run only once, ever, that's the point of static initializers: They run the moment you so much as look funny at that a class (do anything with it at all), and after they've run they are never run again.
Your question is quite unclear, so I'm just taking wild stabs here.
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