原文:https://blog.csdn.net/qq_34926773/article/details/83419004 BigDecimal类型的数据,需要比较大小:声明BigDescimal: BigDescimal bd = new BigDescimal(str1); Integer a = bd1.compareTo(bd2); a = -1,表示bd1小于bd2: a = 0,表示bd1等于bd2: a = 1,表示bd1大于bd2: 所以判断 BigDecimal判断是否为0:
oracle中,任何字符串与null比较得到的结果都是null,而 oracle的判断条件为null时就退出判断(?) 因此判断某个字符串是否在一个集合中时,not in 和 in的结果完全不一样,如 select * from airport_heliport t where t.airport_heliport_uuid in ( select 'e6513669-8cb7-41d9-85af-11ab26930790' from dual union select null from d
关于双重检验锁首先简单来看一个小例子: public class Singleton{ private static Singleton instance = null; private Singleton(){} public static Singleton getInstance(){ if (instance == null) {//e1 synchronized(Singleton.class){ if (instance == null) {//e2 instance = new S
分析forEach的源码会发现:foreach源码例子: public class Foreach { public static void main(String[] args) { List<String> strings = new ArrayList<>(); strings.add("Alis"); for (String name:strings){ System.out.println(name); } } } 用 idea 自带的反编译 publ
sql server 替换null:isnull(arg,value) 如:select isnull(price,0.0) from orders ,如果price为null的话,用0.0替换 与null比较: is not null,is null 如 select * from orders where price is null ,price等于null 如: select * from orders where price is not null ,price不等于null Oracl