我可以使用compareTo对整数和双精度值进行排序吗? [英] Can I use compareTo to sort integer and double values?
问题描述
我可以使用compareTo对整数和双精度值进行排序吗?我的系统给了我一个错误,我不能在原始类型int上调用compareTo(int)。任何想法?
Can I use compareTo to sort integer and double values? My system gives me an error that I Cannot invoke compareTo(int) on the primitive type int. any ideas?
代码:
public int compare(Object o1, Object o2) {
Record o1C = (Record)o1;
Record o2C = (Record)o2;
return o1C.getPrice().compareTo(o2C.getPrice());
}
class Record
public class Record {
String name;
int price;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getPrice() {
return price;
}
public void setPrice(int price) {
this.price = price;
}
}
推荐答案
好,编译器的权利:)你不能直接调用 compareTo
。但是,根据您使用的Java版本,您可以使用 Integer.compare
(1.7中介绍)和 Double.compare
(在1.4中引入)。
Well, the compiler's right :) You can't call compareTo
directly. However, depending on the version of Java you're using, you can use Integer.compare
(introduced in 1.7) and Double.compare
(introduced in 1.4).
例如:
return Integer.compare(o1C.getPrice(), o2C.getPrice());
如果您不在1.7并且仍想使用内置方法,那么可以使用:
If you're not on 1.7 and still want to use built-in methods, you could use:
Integer price1 = o1C.getPrice();
Integer price2 = o2C.getPrice();
return price1.compareTo(price2);
...但这将使用不必要的装箱。鉴于对大型集合进行排序可以进行相当多的比较,这并不理想。在您准备使用1.7之前,可能值得重写比较
。这很简单:
... but this will use unnecessary boxing. Given that sorting a large collection can perform really quite a lot of comparisons, that's not ideal. It may be worth rewriting compare
yourself, until you're ready to use 1.7. It's dead simple:
public static int compare(int x, int y) {
return x < y ? -1
: x > y ? 1
: 0;
}
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