java List的相关工具类

1、

 <dependency>
     <groupId>com.google.guava</groupId>
     <artifactId>guava</artifactId>
     <version>18.0</version>
 </dependency>

2、java代码

 package xxxxxx;

 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;

 import org.apache.commons.lang.StringUtils;

 import com.google.common.base.Function;
 import com.google.common.collect.ArrayListMultimap;
 import com.google.common.collect.ListMultimap;

 public class ListUtils {

     /**
      * list 中有一个为主键key
      *
      * @param list
      * @param function
      * @return
      */
     public static <K, V> Map<K, V> listToMap(List<V> list, Function<V, K> function) {
         Map<K, V> map = new HashMap<K, V>();
         if (list == null)
             return map;
         for (V value : list) {
             K k = function.apply(value);
             map.put(k, value);
         }
         return map;
     }

     /**
      * list 元素转为另一个元素的list
      */
     public static <F, R> List<R> listConvert(List<F> list, Function<F, R> function) {
         List<R> listN = new ArrayList<R>();
         if (list == null)
             return listN;
         for (F value : list) {
             R r = function.apply(value);
             if (r != null)
                 listN.add(r);
         }
         return listN;
     }

     /**
      * list 元素过滤另一个元素的list
      */
     public static <F> List<F> filter(List<F> list, Function<F, Boolean> function) {
         List<F> listN = new ArrayList<F>();
         if (list == null)
             return listN;
         for (F value : list) {
             Boolean r = function.apply(value);
             if (r)
                 listN.add(value);
         }
         return listN;
     }

     /**
      * list 元素转为另一个元素的list并且去重,适合list数据量较小
      */
     public static <F, R> List<R> listConvertAndUnique(List<F> list, Function<F, R> function) {
         List<R> listN = new ArrayList<R>();
         if (list == null)
             return listN;
         for (F value : list) {
             R r = function.apply(value);
             if (r != null && !listN.contains(r))
                 listN.add(r);
         }
         return listN;
     }

     /**
      * list 元素转为以seg分割的字符串
      */
     public static String split(List list, String seg) {
         StringBuilder sb = new StringBuilder();
         for (Object value : list) {
             sb.append(value.toString() + seg);
         }
         String t = sb.toString();
         if (t.endsWith(seg)) {
             int end = t.length() - seg.length();
             t = t.substring(0, end);
         }
         return t;
     }

     public static <V> Map<Integer, V> listToMapByHashCode(List<V> list) {
         Map<Integer, V> map = new HashMap<Integer, V>();
         for (V value : list) {
             map.put(Integer.valueOf(value.hashCode()), value);
         }
         return map;
     }

     public static <K, V> Map<K, V> listToMapByFunction(List<V> list,Function<V,K> function) {
         Map<K, V> map = new HashMap<K, V>();
         for (V value : list) {
             map.put(function.apply(value), value);
         }
         return map;
     }

     // list to ListMultimap
     public static <K, V> ListMultimap<K, V> listToListMultiMap(List<V> list, Function<V, K> function) {
         ListMultimap listMultimap = ArrayListMultimap.<K, V> create();
         for (V value : list) {
             listMultimap.put(function.apply(value), value);
         }
         return listMultimap;
     }

     public static <V> List<V> pageList(List<V> list, int pageIndex, int pageNum) {
         int size = list.size();
         int fromIndex = pageIndex * pageNum;
         if (fromIndex > size) {
             fromIndex = size;
         }
         int toIndex = fromIndex + pageNum;
         if (toIndex > size) {
             toIndex = size;
             return list.subList(fromIndex, toIndex);
         }

         return list.subList(fromIndex, toIndex);
     }

     public static <E> boolean isEmpty(List<E> list) {

         return list == null || list.isEmpty();
     }

     public static List<String> list(String s, String spe) {

         ArrayList<String> list = new ArrayList<>();
         if (StringUtils.isBlank(s))
             return list;
         String[] e = s.split(spe);
         for (String i : e) {
             list.add(i);
         }
         return list;

     }

     public static <T> List<T> toList(T... a) {

         if (a == null)
             return null;
         List<T> l = new ArrayList<>();
         for (T e : a) {
             l.add(e);
         }

         return l;
     }

     /**
      * 通过某个字段进行排序
      */
     public static <K, V> List<V> sortList(List<V> list) {

         return null;
     }

 }

3、在需要的类中调用即可

 List<UserAccountDto> maList = null; //实际不能辅助为null，应该获取一个list实例
 List<TopMobileAccountVo> mavoList = ListUtils.listConvert(maList,new Function<UserAccountDto, TopMobileAccountVo>() {
     public TopMobileAccountVo apply(UserAccountDto ma) {
         TopMobileAccountVo vo = new TopMobileAccountVo();
         vo.convertPOToVO(ma);
         return vo;
     }
 });