How to say“A Class of Class<？>列出< The class>"在Java中？ [英] How to say "A Map of Class<?> to List<The class>" in Java?

问题描述

假设我有一个

  HashMap<？，List<>> map = new HashMap<>（）; 
 map.put（String.class，new ArrayList< Long>（））; 
  

以下代码将被编译。

但是，我想编译失败，因为ArrayList不适用于String类型。

另外，我的通配符仅限于某个特定的接口（例如Exception），所以我想我应该把< ;?扩展异常> 某处。

如何实现上述功能？测试：

  map.put（String.class，new ArrayList< String>（））; //因为String不是一个异常而失败
 map.put（IOException.class，new ArrayList< FileNotFoundException>（））; // File失败，因为FileNotFoundException不是IOException，即使它是它的子类
 map.put（FileNotFoundException.class，new ArrayList< IOException>（））; //我想我对此很好。 
 map.put（IllegalArgumentException.class，new ArrayList< IllegalArgumentException>（））; //成功
 map.put（NumberFormatException.class，new ArrayList< ServerException>（））; //再次失败，因为两个类不匹配
 map.put（ClientDecodingException.class，new ArrayList< ClientDecodingException.class>）; //因为映射采用通配符，所以再次成功例外
  

解决方案

我已经通过使用raw Class 和 List （仍然不能修复此问题） ），并通过使用映射包装来存储 Exception ：

  public class ExceptionMapWrapper {
 
 private Map< Class，List> MYMAP; 
 
 public ExceptionMapWrapper（）{
 myMap = new HashMap<>（）; 
} 
 //测试的相关方法：put和get 
 public< T extends Exception> void put（Class< T> clazz，List< T> list）{
 myMap.put（clazz，list）; 
} 
 
 public< T extends Exception>列表与LT; T> get（Class< T> key）{
返回myMap.get（key）; 
 
 
 $ / code $ / pre 
 
 
以及一个简单的测试： 
 
 
  ExceptionMapWrapper exceptionMapWrapper = new ExceptionMapWrapper（）; 
 Class< IOException> clazz = IOException.class; 
列表< IOException> list = new ArrayList<>（）; 
 exceptionMapWrapper.put（clazz，list）; 
 //编译器错误，取消注释以查看它们
 //exceptionMapWrapper.put(String.class，new ArrayList< String>（））; 
 //exceptionMapWrapper.put（IOException.class，new ArrayList< ClassCastException>（））; 
 //exceptionMapWrapper.put（IOException.class，new ArrayList< SQLException>（））; 
列表< IOException> ioExList = exceptionMapWrapper.get（clazz）; 
 //编译器错误，取消注释
 //列表< SQLException> sqlExList = exceptionMapWrapper.get（clazz）; 
  
 
Say I have a 
HashMap<?, List<?>> map = new HashMap<>();
map.put(String.class, new ArrayList<Long>());
The following code will compile.

However, I want to fail compilation because the ArrayList is not for String type.

Also, my wildcard is limited to some specific interface (e.g. Exception), so I suppose I should put that <? extends Exception> somewhere.

How can I achieve the above?

Example Test:
map.put(String.class, new ArrayList<String>()); //Fail because String is not an Exception
map.put(IOException.class, new ArrayList<FileNotFoundException>()); // Fail because FileNotFoundException is not an IOException even though it is a subclass of it
map.put(FileNotFoundException.class, new ArrayList<IOException>()); // I suppose I'm fine with this.
map.put(IllegalArgumentException.class, new ArrayList<IllegalArgumentException>()); // Succeed
map.put(NumberFormatException.class, new ArrayList<ServerException>()); // Fail again because the two classes don't match
map.put(ClientDecodingException.class, new ArrayList<ClientDecodingException.class>); // Succeed again since the map takes in a wildcard Exception

解决方案
I've done this by using raw Class and List (still cannot fix this) and by using a map wrapper for storing Exception only:
public class ExceptionMapWrapper {

    private Map<Class, List> myMap;

    public ExceptionMapWrapper() {
        myMap = new HashMap<>();
    }
    //relevant methods for the test: put and get
    public <T extends Exception> void put(Class<T> clazz, List<T> list) {
        myMap.put(clazz, list);
    }

    public <T extends Exception> List<T> get(Class<T> key) {
        return myMap.get(key);
    }
}
And a simple test for this:
ExceptionMapWrapper exceptionMapWrapper = new ExceptionMapWrapper();
Class<IOException> clazz = IOException.class;
List<IOException> list = new ArrayList<>();
exceptionMapWrapper.put(clazz, list);
//compiler errors, uncomment to see them
//exceptionMapWrapper.put(String.class, new ArrayList<String>());
//exceptionMapWrapper.put(IOException.class, new ArrayList<ClassCastException>());
//exceptionMapWrapper.put(IOException.class, new ArrayList<SQLException>());
List<IOException> ioExList = exceptionMapWrapper.get(clazz);
//compiler error, uncomment to see
//List<SQLException> sqlExList = exceptionMapWrapper.get(clazz);


                        
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