轉載地址:https://www.cnblogs.com/linjiqin/p/3425572.html
//如果object爲null,則設置爲defaultValue
ObjectUtils.defaultIfNull(object, defaultValue);
//判斷集合是否爲null
List<String> list=new ArrayList<String>();
System.out.println(list.isEmpty()); //true
System.out.println(list.size()); //0
Set<String> set=new HashSet<String>();
System.out.println(set.isEmpty()); //true
System.out.println(set.size()); //0
Map<String, String> map=new HashMap<String, String>();
System.out.println(map.isEmpty()); //true
System.out.println(map.size()); //0
方法一(數據量大,效率低):
if(list!=null && list.size()>0){
}
方法二(數據量大,效率高):
if(list!=null && !list.isEmpty()){
}