java - 类型不匹配 : cannot convert from element type Object to int

Question

我在显示 ht.keySet() 的行中收到以下错误:

Type mismatch: cannot convert from element type Object to int

ht 是 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);
    }
}

Answer 1

您需要使用 Java generics .

声明ht作为LinkedHashMap<Integer, Foo>其中 Foo是您希望 ht.get() 返回的任何数据类型.使用 Map界面会更好:

LinkedHashMap<Integer, Foo> ht = new LinkedHashMap<Integer, Foo>();
// or preferably
Map<Integer, Foo> ht = new LinkedHashMap<Integer, Foo>();