英文:
(Subjective) Invalid Java Class Constructor
问题
我正在编写一个Java类，其中给定的参数可能无效，但仍然是正确的类型。我希望我的类接受两个整数，但不允许第二个整数为零。我有哪些可能性来中断构造函数，也许手动返回null？我的可能性有哪些？
public class Test {
private int a, b;
public Test(int p1, int p2) {
if (p2 == 0) {
// Do something to handle the invalid parameter, such as throwing an exception.
} else {
a = p1;
b = p2;
}
}
}
英文:
I am programming a java class, where the given parameters could be invalid, but still be the right type. I want my class to take two integers, but the second one is not allowed to be zero. What do I have for possibilities to interrupt the Constructor, maybe returning manually null? What are my possibilities?
public class Test {
private a, b;
public Test(p1, p2) {
if (p2 == 0) return null;
a = p1;
b = p2;
}
}
答案1
得分: 2
构造函数没有返回值，因此返回 `null` 不是一个选项。惯用的做法是抛出 [`IllegalArgumentException`](https://docs.oracle.com/javase/8/docs/api/java/lang/IllegalArgumentException.html)：
```java
public class Test {
private a, b;
public Test(p1, p2) {
if (p2 == 0) {
throw new IllegalArgumentException("p2 不能为零");
}
a = p1;
b = p2;
}
}
英文:
A constructor doesn't have a return value, so returning null isn't an option. The idiomatic thing to do would be to throw an IllegalArgumentException:
public class Test {
private a, b;
public Test(p1, p2) {
if (p2 == 0) {
throw new IllegalArgumentException("p2 can't be null");
}
a = p1;
b = p2;
}
}
答案2
得分: 2
如果您想在参数无效的情况下返回 null，不能使用构造函数。
相反，将构造函数设置为私有，并编写一个静态工厂方法：
private Test(int a, int b) {
// 任何操作。
}
public static Test create(int a, int b) {
if (/* a 和 b 无效 */) {
return null;
}
return new Test(a, b);
}
然后，您应该调用 Test.create 而不是 new Test。
但前提是您不打算扩展 Test。
英文:
If you want to return null in the case of invalid parameters, you can't use a constructor.
Instead, make the constructor private, and write a static factory method:
private Test(int a, int b) {
// Whatever.
}
public static Test create(int a, int b) {
if (/* a and b are invalid */) {
return null;
}
return new Test(a, b);
}
You then invoke Test.create instead of new Test.
This is only an option if you don't want to extend Test, though.
答案3
得分: 0
根据您的需要，有很多可能性，这是最重要的事情。
一个想法可能是，如果第二个参数为0，就抛出IllegalArgumentException异常，这样构造函数会以错误退出，而类不会被创建。
英文:
Quite a lot of possibilities, depending on what you need, which is the most important thing.
An idea could be throw an IllegalArgumentException if the 2nd parameter is 0 so the constructor exits with error and the class is not created.
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