java – 我怎么能在地图中说“这两个泛型类型是一样的”？

public interface IToStringService<T> {
    public String toString( T value );
}

代码如下所示：

// (1) How can I say that these two wildcards must in fact be the same type?
private Map<Class<?>,IToStringService<?>> specialHandlers = Maps.newHashMap();

// Generic method,must accept Object (any type really)
@Override
public String toString( Object value ) {

    if( null == value ) {
        return "null";
    }

    Class<?> type = value.getClass();
    if( type.isArray() ) {
        return arrayToString( value );
    }

    // (2) How can I get rid of this SuppressWarnings?
    @SuppressWarnings( "unchecked" )
    IToStringService<Object> handler = (IToStringService<Object>) specialHandlers.get( type );

    if( null != handler ) {
        return handler.toString( value );
    }

    return value.toString();
}

public <T> void addSpecialHandler( Class<T> type,IToStringService<T> handler ) {
    specialHandlers.put( type,handler );
}

一个实现看起来像这样：

@SuppressWarnings( "rawtypes" ) // Can't add generics to "Class" or I get compile errors when calling DefaultToStringService.addSpecialHandler() :-(
public class ClassToStringService implements IToStringService<Class> {

    @Override
    public String toString( Class value ) {
        return value == null ? "null" : value.getName();
    }
}

我有几个问题：

>我怎么能说specialHandlers映射中的处理程序必须匹配用作键的类型？
>如何在方法中使用相同的信息以避免强制转换和@SuppressWarnings？
>当我更改ClassToStringService以实现IToStringService< Class<？>>时,在调用addSpecialHandler时会遇到编译错误(Class.class,new ClassToStringService());我该如何解决这个问题？