Set、List和数组互相转换

亦凉 2022-05-09 00:42 259阅读 0赞

### java中Set、List和数组互相转换 ###

public class ArraysTest { 
    
      /** * 数组转List * @param arrays * @return */
      private static List arraysToList(Object[] arrays) { 
        return Arrays.asList(arrays); // 返回一个固定长度的list，不可add和remove，否则会报java.lang.UnsupportedOperationException
        // 如果想要返回可变列表，则需要将数组里的元素遍历加到List中
        /*List list = new ArrayList(); if (arrays != null && arrays.length > 0) { for (Object obj : arrays) { list.add(obj); } } return list;*/
      }
    
    
      /** * 数组转set * @param arrays * @return */
      private static Set arraysToSet(Object[] arrays) { 
        return new HashSet(Arrays.asList(arrays)); // 先转成list，再通过HashSet构造出Set
      }
    
      /** * list转数组 * @param list * @return */
      private static Object[] listToArrays(List list) { 
        return list.toArray();
      }
    
      /** * list转set * @param list * @return */
      private static Set listToSet(List list) { 
        return new HashSet(list);
      }
    
      /** * set转数组 * @param set * @return */
      private static Object[] setToArray(Set set) { 
        return set.toArray();
      }
    
      /** * set转List * @param set * @return */
      private static List setToList(Set set) { 
        return new ArrayList(set);
      }
      
    
      public static void main(String[] args) { 
        String[] strArrays = new String[]{ "csdn", "ddp", "Roman", "ForEver"};
        List list1 = arraysToList(strArrays);
        Set set = arraysToSet(strArrays);
        Object[] objArrays = listToArrays(list1);
        Set set1 = listToSet(list1);
        Object[] objectArrays2 = setToArray(set1);
        List list2 = setToList(set1);
        System.out.println("sss");
      }
      
    
      private static void printList(List list) { 
        if (list != null && list.size() > 0) { 
          for (Object obj : list) { 
            System.out.println(obj.toString());
          }
        }
      }
    }