java - 如何重写以下方法而不出现未经检查的警告？

Question

private <K> Map<K, Object> createMap(final Class<K> keyClass) {
    final boolean isEnum = keyClass.isEnum();

    if(isEnum) {
                    // The following two lines throw warnings
        final Class<? extends Enum<?>> enumCls = (Class<? extends Enum<?>>)keyClass;
        final Map<K, Object> map = (Map<K, Object>)new EnumMap(enumCls);

        return map;
    }
    else{
        final Map<K, Object> map = new HashMap<K, Object>();
        return map;
    }
}

警告

found   : java.lang.Class<K>
required: java.lang.Class<? extends java.lang.Enum<?>>
        final Class<? extends Enum<?>> enumCls = (Class<? extends Enum<?>>)keyClass;
                                                                           ^
T.java:9: warning: [unchecked] unchecked call to EnumMap(java.lang.Class<K>) as a member of the raw type java.util.EnumMap
        final Map<K, Object> map = (Map<K, Object>)new EnumMap(enumCls);
                                                   ^
T.java:9: warning: [unchecked] unchecked cast                                   
found   : java.util.EnumMap                                                     
required: java.util.Map<K,java.lang.Object>                                     
        final Map<K, Object> map = (Map<K, Object>)new EnumMap(enumCls);
                                                   ^
3 warnings

Answer 1

编译器无法执行某些检查，并且会向您发出警告。在此方法中避免这些的唯一方法是在方法之前添加注释

@SuppressWarnings("unchecked")

即使是像 ArrayList 这样的集合，在编译时也会出现警告。