import java.util.*;public class CollectionUtil {    /**     * 对List进行分页处理     * @param list 需要分页的List     * @param pageSize 单页条数     * @param pageNum 页码     */    public static 
    
      List
     
       pageList(List
      
        list, int pageSize, int pageNum) {        if (list == null || list.isEmpty()) {            return list;        }        int offset = (pageNum - 1) * pageSize;        int size = Math.min(pageNum * pageSize, list.size());        if (offset > size) {            return Collections.emptyList();        }        return list.subList(offset, size);    }    /**     * 匹配Map中是否存在key，忽略大小写     * @param map 要遍历的Map     * @param key 要匹配的Key     * @return 命中Map中的Key     */    public static String matchKeyIgnoreCase(Map
       
         map, String key) {        if (map == null || map.isEmpty() || key == null) {            return null;        }        for (String mapKey : map.keySet()) {            if (mapKey.equalsIgnoreCase(key)) {                return mapKey;            }        }        return null;    }    /**     * 对List元素去重     */    public static 
        
          List
         
           uniqueList(List
          
            list) { if (list == null || list.isEmpty()) { return list; } Set
           
             set = new HashSet<>(list); list.clear(); list.addAll(set); return list; }}