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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
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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
摘要:
/* * Copyright (c) 1997, 2017, Oracle and/or its affiliates. All rights reserved. * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. 阅读全文