[英]Java Inheritance and generics, how to declare a function that applies to “multiple types” of inheritance?
I couldn't find a good question/title for what I want to do. 我找不到一个好的问题/标题我想做什么。 I'm not very familiar with generics, so I have some issues understanding how they work.
我对泛型不是很熟悉,所以我有一些问题需要了解它们是如何工作的。
Say I have a Map<k,v>
class that maps keys to values. 假设我有一个
Map<k,v>
类,它将键映射到值。
class Map<K,V>{
public V get(K key){
//...
}
public void set(K key, V v){
//...
}
}
Then, I create two subclasses: 然后,我创建了两个子类:
class SuperMap<K,V> extends Map<K,V>{ /* ... */ }
class HyperMap<K,V> extends Map<K,V>{ /* ... */ }
What I want is to create a function that can take any map and print the string representation of each key and value. 我想要的是创建一个函数,可以采取任何映射并打印每个键和值的字符串表示形式。 So I could just:
所以我可以:
SuperMap<Unicorn, Horse> unicornsMap = ....;
HyperMap<Pegasus, Horse> pegasusMap = ....;
printMap(unicornsMap);
printMap(pegasusMap);
So, what should be the printMap
function signature? 那么,
printMap
函数签名应该是什么?
I tried with: void printMap(Map<Object, Horse>)
But it doesn't work: 我试过:
void printMap(Map<Object, Horse>)
但它不起作用:
The method
printMap(Map<Object,Horse>)
in the type MainClass is not applicable for the arguments (HyperMap<Pegasus,Horse>
)printMap(Map<Object,Horse>)
类型中的方法printMap(Map<Object,Horse>)
不适用于参数(HyperMap<Pegasus,Horse>
)The method
printMap(Map<Object,String>)
in the type MainClass is not applicable for the arguments (SuperMap<Unicorn,Horse>
)printMap(Map<Object,String>)
类型中的方法printMap(Map<Object,String>)
不适用于参数(SuperMap<Unicorn,Horse>
)
printMap(Map<?, Horse>)
或者,或者
<K> printMap(Map<K, Horse>)
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