英文:
Is there a way of making optional atributes in java?
问题
我需要在Java中编写这个类。我考虑过创建一堆构造函数，但我不认为那是最好的方法。我想知道Java是否有某种可选参数或属性，以使这更简单。
英文:
I need to code this class in java. I thought of making a bunch of constructors but i dont think thats the best way to do it. Id like to know if java has some sort of optional parameters or attributes to make this simpler.
答案1
得分: 0
你可以使用一个带有可变参数（varargs）的构造函数来实现，因为你的类中所有字段的类型都是 String：
public class Address {
private String street;
private String city;
private String postalCode;
private String state;
private String country;
public Address(String... params) {
street = params[0];
city = params[1];
//等等。在调用构造函数时，请确保按照赋值顺序传递参数。还要首先检查 varargs 的大小，
//以免分配不存在的参数。
}
}
然后可以像这样调用它，仅设置街道和城市：
Address address = new Address("myStreet", "myCity");
另一种选择是使用一个带有所有参数的构造函数，如果你不想设置某个值，请在对应参数的位置传递 null 到构造函数中：
Address address = new Address("myStreet", "myCity", null, null, null);
英文:
You can do it with one constructor with varargs, since all fields of your class are of type String:
public class Address {
private String street;
private String city;
private String postalCode;
private String state;
private String country;
public Address(String... params) {
street = params[0];
city = params[1];
//etc. Just take care to pass the arguments in the order you are
//assigning them when you call the constructor. Also check the size
//of varargs first so you don't assign arguments that don't exist.
}
}
And then call it like so to set only the street and city:
Address adress = new Address("myStreet", "myCity");
An alternative is to have one constructor with all the arguments, and if you don't want to set a value, pass null to the constructor in place of the corresponding parameter:
Address adress = new Address("myStreet", "myCity", null, null, null);
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