Java对象转型的相关内容

JAVA对象的转型

父类引用指向子类对象，我们称这个过程为向上转型，属于自动类型转换。向上转型后的父类引用变量只能调用它编译类型的方法，不能调用它运行时类型的方法。这时，我们就需要进行类型的强制转换，我们称之为向下转型!对象的转型：public class...

[帮助文档] 如何使用Java堆分析对象查询语言OQL

1. OQL语法OQL语法如下：SELECT * FROM [ INSTANCEOF ] [ WHERE ]2. 语法各子句说明select部分SELECT toString(x), x.value, x....

「大师课」搞定 Java 开发基础

23 课时 |

8714 人已学 |

加入学习

Java Spring Boot 2.6.0开发实战-1024程序员节创造营公益课

5 课时 |

1162 人已学 |

加入学习

Java Web开发-Web应用、Tomcat、HTTP请求与响应

17 课时 |

1440 人已学 |

加入学习

Java多态——对象的上下转型

一、概念由子类转型成父类，在继承图上是向上移动的，一般称为向上转型上一篇文章的代码就是向上转型Animal a1 = new Dog();Animal a1 = new (Animal)Dog(); //实际上就是强转，但是一般不需要写出来向上转型是从一个较专用类型向通用类型转换，所以总是安全的（体...

[帮助文档] 管道任务同步读取源表时报错java.sql.SQLExceptionORA-08103

问题描述Dataphin管道任务同步读取源表时，报错“java.sql.SQLException: ORA-08103: 对象不再存在”;源表是存在的。问题原因管道任务同步读取源表时，另一个用户在全量更新该源表，即有一个进程truncate，insert动作，而同时有另一进程对同一表做select动...

Java实用教程系列之对象的转型

Java今日分享实用的Java教程之对象的转型体现：父类的引用可以指向子类的对象接口的引用可以指向实现类的对象转型：向上转型由子类类型转型为父类类型，或者由实现类类型转型为接口类型向上转型一定会成功，是一个隐式转换向上转型后的对象，将只能访问父类或者接口中的成员向下转型由父类类型转型为子类类型...

java对象转型问题

java对象转型问题求解答这个不太明白，求具体例子说明，看了网上的一些举例介绍说明还是不太明白实际意义是干嘛，做项目能实际应用到哪里

共有6条

< 1 >

跳转至： GO

更新时间 2023-09-06 22:00:55

本页面内关键词为智能算法引擎基于机器学习所生成，如有任何问题，可在页面下方点击"联系我们"与我们沟通。

产品推荐

{"optioninfo":{"dynamic":"ture","static":"true"},"simplifiedDisplay":"newEdition","newCard":[{"ifIcon":"img","link":"https://img.alicdn.com/tfs/TB1XY8hGYr1gK0jSZFDXXb9yVXa-1740-328.png","icon":"","iconImg":"https://img.alicdn.com/tfs/TB1iJox2Br0gK0jSZFnXXbRRXXa-200-200.png","contentLink":"https://www.aliyun.com/product/arms","title":"应用实时监控服务 ARMS","des":"应用实时监控服务ARMS 包含前端监控，应用监控、云拨测等模块，覆盖小程序、APP、网站等客户端及ECS、Serverless、容器等环境，为分布式、微服务应用提供端到端性能监控与全链路追踪诊断， 让运维监控更加高效便捷。","link1":"https://common-buy.aliyun.com/?spm=5176.26849858.J_5253785160.3.3887564cBbVoUd&commodityCode=arms_serverless_public_cn","btn1":"立即开通（每月50GB额度）","link2":"https://common-buy.aliyun.com/?spm=5176.8140086.1280672.buy11.30f2bb91uujI1A&commodityCode=arms_app_bag#/buy","btn2":"资源包购买（旧版计费）","btn3":"帮助文档","link3":"https://help.aliyun.com/zh/arms/application-monitoring/getting-started/overview?spm=a2c4g.11186623.0.0.502edf6bVmoHkw","infoGroup":[{"infoName":"最佳实践","infoContent":{"firstContentLink":"https://www.aliyun.com/activity/middleware/ObservabilityConference2022?spm=5176.26849857.J_5253785160.2.1f4415e9ite0CU","firstContentName":"新老用户限时钜惠","lastContentLink":"https://www.aliyun.com/activity/middleware/observability","lastContentName":"最新实践 & 公开课"}},{"infoName":"相关推荐","infoContent":{"firstContentLink":"https://www.aliyun.com/activity/middleware/Application_monitoring?spm=5176.8140086.J_4084816840.3.1db8be45A6RecL","firstContentName":"应用监控-Java监控","lastContentName":"前端监控-Web应用监控","lastContentLink":"https://www.aliyun.com/activity/middleware/web_monitoring?spm=5176.26849857.J_9938243310.4.640115e9rV41KE"}},{"infoName":"产品入门","infoContent":{"firstContentName":"快速接入","lastContentName":"计费说明","firstContentLink":"https://help.aliyun.com/zh/arms/application-monitoring/getting-started/monitor-java-applications-1/?spm=a2c4g.11186623.0.0.36badf6bscAkU3","lastContentLink":"https://help.aliyun.com/zh/arms/application-monitoring/product-overview/billing-description?spm=a2c4g.11186623.0.0.41ba1a08NHoPA3"}},{"infoName":"相关推荐","infoContent":{"firstContentName":" 云拨测-网络测速","firstContentLink":"https://www.aliyun.com/activity/middleware/website/performance/test?spm=5176.20960838.0.0.6d33305emfVIyC","lastContentLink":"","lastContentName":""}}]}],"card":[],"search":[],"infoCard":[{"bannerUrl":"https://img.alicdn.com/tfs/TB1Xf81a3gP7K4jSZFqXXamhVXa-5169-974.jpg","bannerTitle":"mPaaS 小程序","bannerContent":"源自于支付宝小程序框架，亿级线上业务体量的锤炼，安全性媲美支付宝原生能力。<br>不仅面向自有 App 投放小程序，更可快速构建打包，覆盖支付宝、淘宝、钉钉等应用。","liveButtonName":"查看详情","liveButtonLink":"https://www.aliyun.com/product/mobilepaas/mpaas-miniprogram","contentTitle":"提供即开即用的端上体验","homePageLink":"https://common-buy.aliyun.com/?spm=5176.14673561.J_8751524360.2.56702709BussF3&commodityCode=mpaas_beta#/open","homePageName":"免费试用","linkGroup":[{"linkContent":"发布包大小极致优化，节省流量和存储。"},{"linkContent":"服务迭代不再受发版限制，快速发布，快速迭代。"},{"linkContent":"业务开发效率更加优秀，一次开发，多端运行。"}]}],"title":{"mainTitle":"应用实时监控服务ARMS","subtitle":"","linkUrl":"","btnText":"查看详情"},"visual":{"topbg":"https://img.alicdn.com/tfs/TB1bQuBIYH1gK0jSZFwXXc7aXXa-3840-740.gif","icon":"","textColor":"dark"},"dataList":[{"summary":"啦啦啦","author":"wuwu","linksUrl":"#"}],"sceneCard":[],"txt":[]}

{"$env":{"JSON":{}},"$page":{"env":"production"},"$context":{"optioninfo":{"dynamic":"ture","static":"true"},"simplifiedDisplay":"newEdition","newCard":[{"ifIcon":"img","link":"https://img.alicdn.com/tfs/TB1XY8hGYr1gK0jSZFDXXb9yVXa-1740-328.png","icon":"","iconImg":"https://img.alicdn.com/tfs/TB1iJox2Br0gK0jSZFnXXbRRXXa-200-200.png","contentLink":"https://www.aliyun.com/product/arms","title":"应用实时监控服务 ARMS","des":"应用实时监控服务ARMS 包含前端监控，应用监控、云拨测等模块，覆盖小程序、APP、网站等客户端及ECS、Serverless、容器等环境，为分布式、微服务应用提供端到端性能监控与全链路追踪诊断， 让运维监控更加高效便捷。","link1":"https://common-buy.aliyun.com/?spm=5176.26849858.J_5253785160.3.3887564cBbVoUd&commodityCode=arms_serverless_public_cn","btn1":"立即开通（每月50GB额度）","link2":"https://common-buy.aliyun.com/?spm=5176.8140086.1280672.buy11.30f2bb91uujI1A&commodityCode=arms_app_bag#/buy","btn2":"资源包购买（旧版计费）","btn3":"帮助文档","link3":"https://help.aliyun.com/zh/arms/application-monitoring/getting-started/overview?spm=a2c4g.11186623.0.0.502edf6bVmoHkw","infoGroup":[{"infoName":"最佳实践","infoContent":{"firstContentLink":"https://www.aliyun.com/activity/middleware/ObservabilityConference2022?spm=5176.26849857.J_5253785160.2.1f4415e9ite0CU","firstContentName":"新老用户限时钜惠","lastContentLink":"https://www.aliyun.com/activity/middleware/observability","lastContentName":"最新实践 & 公开课"}},{"infoName":"相关推荐","infoContent":{"firstContentLink":"https://www.aliyun.com/activity/middleware/Application_monitoring?spm=5176.8140086.J_4084816840.3.1db8be45A6RecL","firstContentName":"应用监控-Java监控","lastContentName":"前端监控-Web应用监控","lastContentLink":"https://www.aliyun.com/activity/middleware/web_monitoring?spm=5176.26849857.J_9938243310.4.640115e9rV41KE"}},{"infoName":"产品入门","infoContent":{"firstContentName":"快速接入","lastContentName":"计费说明","firstContentLink":"https://help.aliyun.com/zh/arms/application-monitoring/getting-started/monitor-java-applications-1/?spm=a2c4g.11186623.0.0.36badf6bscAkU3","lastContentLink":"https://help.aliyun.com/zh/arms/application-monitoring/product-overview/billing-description?spm=a2c4g.11186623.0.0.41ba1a08NHoPA3"}},{"infoName":"相关推荐","infoContent":{"firstContentName":" 云拨测-网络测速","firstContentLink":"https://www.aliyun.com/activity/middleware/website/performance/test?spm=5176.20960838.0.0.6d33305emfVIyC","lastContentLink":"","lastContentName":""}}]}],"card":[],"search":[],"infoCard":[{"bannerUrl":"https://img.alicdn.com/tfs/TB1Xf81a3gP7K4jSZFqXXamhVXa-5169-974.jpg","bannerTitle":"mPaaS 小程序","bannerContent":"源自于支付宝小程序框架，亿级线上业务体量的锤炼，安全性媲美支付宝原生能力。<br>不仅面向自有 App 投放小程序，更可快速构建打包，覆盖支付宝、淘宝、钉钉等应用。","liveButtonName":"查看详情","liveButtonLink":"https://www.aliyun.com/product/mobilepaas/mpaas-miniprogram","contentTitle":"提供即开即用的端上体验","homePageLink":"https://common-buy.aliyun.com/?spm=5176.14673561.J_8751524360.2.56702709BussF3&commodityCode=mpaas_beta#/open","homePageName":"免费试用","linkGroup":[{"linkContent":"发布包大小极致优化，节省流量和存储。"},{"linkContent":"服务迭代不再受发版限制，快速发布，快速迭代。"},{"linkContent":"业务开发效率更加优秀，一次开发，多端运行。"}]}],"title":{"mainTitle":"应用实时监控服务ARMS","subtitle":"","linkUrl":"","btnText":"查看详情"},"visual":{"topbg":"https://img.alicdn.com/tfs/TB1bQuBIYH1gK0jSZFwXXc7aXXa-3840-740.gif","icon":"","textColor":"dark"},"dataList":[{"summary":"啦啦啦","author":"wuwu","linksUrl":"#"}],"sceneCard":[],"txt":[]}}