英文:
unable to use constructor in java
问题
我已经开始学习Java泛型，并且这是我的优先队列实现：
public class MinPQ<Key> implements Iterable<Key> {
private Key[] pq; // 在索引1到n存储项目
private int n; // 优先队列上的项目数
private Comparator<Key> comparator; // 可选比较器
public MinPQ(Key[] keys) {
n = keys.length;
pq = (Key[]) new Object[keys.length + 1];
//......
//......
}
}
这是我的主类：
public class Demo {
public static void main(String[] args) {
// TODO Auto-generated method stub
int[] ar = {1,2,3};
MinPQ<Integer> pq = new MinPQ<Integer>(ar);
}
}
但是在这里我得到一个错误，错误消息是**"The constructor MinPQ(int[]) is undefined"**，请问有人能帮我找到问题所在吗？
英文:
I have started learing java generics and this is my priority queue implementation:
public class MinPQ<Key> implements Iterable<Key> {
private Key[] pq; // store items at indices 1 to n
private int n; // number of items on priority queue
private Comparator<Key> comparator; // optional comparator
public MinPQ(Key[] keys) {
n = keys.length;
pq = (Key[]) new Object[keys.length + 1];
.....
.....
}
}
And this is my main class :
public class Demo {
public static void main(String[] args) {
// TODO Auto-generated method stub
int[] ar = {1,2,3};
MinPQ<Integer> pq = new MinPQ<Integer>(ar);
}
}
But here I get an error stating "The constructor MinPQ(int[]) is undefined" can someone please help me find the issue here ?
答案1
得分: 1
你不能在泛型中使用原始类型。只需将以下代码：
int[] ar = {1,2,3};
改为：
Integer[] ar = {1,2,3};
或者使用以下方法进行封装：
IntStream.of(ar).boxed().toArray(Integer[]::new)
基本上，你正试图将一个 int[] 传递给一个需要 Integer[] 的构造函数，这是因为 MinPQ<Integer> 的声明。因此，理论上，如果你将其声明为 MinPQ<int>，它应该可以工作- 但正如开头所述，我们不能在泛型中使用原始类型。
英文:
You can't use primitive types with generics. Just change:
int[] ar = {1,2,3};
to:
Integer[] ar = {1,2,3};
or box it with
IntStream.of(ar).boxed().toArray(Integer[]::new)
Basically you're trying to pass an int[] to a constructor which requires Integer[], because of MinPQ<Integer> declaration. So, in tehory it should work if you declared it as MinPQ<int> - but as stated at the beginning we can't use primitive types for generics.
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