带实体的 Collection 转换为 List 集合

	    
//求并集--a和b是自己创建的实体List集合 T实体类
Collection<T> union= CollectionUtils.union(a,b);
        
//Collection转化成List
 Iterator<T> iterator = union.iterator();
          Collection<T> entityList =new ArrayList<>();
            while (iterator .hasNext()){
                T needEntity= iterator.next();
                entityList.add(needEntity);
            }
  System.out.println(entityList);