摘要:
1,错误用法 a.equals(b) //a 是null, 抛出NullPointException异常 2,正确用法 Objects.equals(a, b) //这种方法对null值进行了条件判断 分析源码 public final class Objects { private Objects 阅读全文
摘要:
DROP PROCEDURE IF EXISTS my_insert; CREATE PROCEDURE my_insert() BEGIN DECLARE n int DEFAULT 1; loopname:LOOP INSERT INTO order_today VALUES (n, n, n+ 阅读全文