java 类型不匹配：无法从元素类型 Object 转换为 int
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Type mismatch: cannot convert from element type Object to int
提问by max
I'm getting the following error on the line where it says ht.keySet():
我在它说的那一行上收到以下错误ht.keySet()：
Type mismatch: cannot convert from element type Object to int
类型不匹配：无法从元素类型 Object 转换为 int
htis a LinkedHashMap.
ht是一个LinkedHashMap。
for (int key : ht.keySet())
{
if(ht.get(key).size() == 0)
{
System.out.println("There is no errors in " + key) ;
}
else
{
System.out.println("ERROR: there are unexpected errors in " + key);
}
}
回答by Matt Ball
You need to use Java generics.
您需要使用Java 泛型。
Declare htas a LinkedHashMap<Integer, Foo>where Foois whatever data type you expect to be returned by ht.get(). Using the Mapinterface would be even better:
将您希望返回的任何数据类型声明ht为LinkedHashMap<Integer, Foo>where 。使用界面会更好：Fooht.get()Map
LinkedHashMap<Integer, Foo> ht = new LinkedHashMap<Integer, Foo>();
// or preferably
Map<Integer, Foo> ht = new LinkedHashMap<Integer, Foo>();
回答by alexblum
It must be: for (Integer key : ht.keySet())...
一定是： for (Integer key : ht.keySet())...
LinkedHashMap<K, V>where K and V are Objects, not primitiv (int, short ...)
LinkedHashMap<K, V>其中 K 和 V 是对象，而不是 primitiv (int, short ...)
回答by amit
ht is a LinkedHashMap, if it contains only Integers, you should declare it as LinkedHashMap<Integer,Object>.
ht 是 a LinkedHashMap，如果它只包含Integers，则应将其声明为LinkedHashMap<Integer,Object>.
If it will be declared as LinkedHashMap<Integer,Object>, the unboxing to an intwill be done automatically.
如果将其声明为LinkedHashMap<Integer,Object>，int则将自动完成对 an 的拆箱。
(*) even better if you declare it as LinkedHashMap<Integer,[actual-object-type]>
(*) 如果你将它声明为更好 LinkedHashMap<Integer,[actual-object-type]>
回答by Ingo
Use Integer instead of int and it will probably work. The keys in the LinkedHashMap must be objects, not primitive types.
使用 Integer 而不是 int ，它可能会起作用。LinkedHashMap 中的键必须是对象，而不是原始类型。
