如何在没有未经检查的警告的情况下重写以下方法？

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

编译器无法进行一些检查,它会给你一个警告.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")

甚至像ArrayList这样的集合也没有在没有警告的情况下编译.