When it's the case that each instance of the class is equal to only itself. 1. Each instance of the class is inherently unique. 2. You don't care whether the class provides a "logical equality" test. 3. If a superclass has already overridden equ…

Failure to do so will result in a violation of the general contract for Object.hashCode, which will prevent your class from functioning properly in conjunction with all hash-based collections, including HashMap, HashSet, and Hashtable. Simple recipe…

Tips <Effective Java, Third Edition>一书英文版已经出版,这本书的第二版想必很多人都读过,号称Java四大名著之一,不过第二版2009年出版,到现在已经将近8年的时间,但随着Java 6,7,8,甚至9的发布,Java语言发生了深刻的变化. 在这里第一时间翻译成中文版.供大家学习分享之用. 40. 始终使用Override注解 Java类库包含几个注解类型.对于典型的程序员来说,最重要的是@Override.此注解只能在方法声明上使用,它表明带此注解的方法声明…

 You must override hashCode in every class that overrides equals.…

本文参考 本篇文章参考自<Effective Java>第三版第十一条"Always override hashCode when you override equals" You must override hashCode in every class that overrides equals hashCode()方法的通用约定如下: When the hashCode method is invoked on an object repeatedly during…

Hi guys, I am happy to tell you that I am moving to the open source world. And Java is the 1st language I have chosen for this migration. It's a nice chance to read some great books like "Effective Java 2nd Edition" and share the note for what I…

<Effective Java>目录摘抄. 我知道这看起来很糟糕.当下,自己缺少实际操作,只能暂时摘抄下目录.随着,实践的增多,慢慢填充更多的示例. Chapter 2 Creating and Destroying Objects Consider static factory methods instead of constructors Consider a builder when faced with many constructor parameters Enforce the s…

本文参考 本篇文章参考自<Effective Java>第三版第十条"Obey the general contract when overriding equals" the conditions when each instance of the class is equal only to itself Each instance of the class is inherently unique -- 类的每一个实例本就彼此不同,例如Thread类,每一个线程仅和自…

Chapter 3 Methods Common to All Objects Item 8: Obey the general contract when overriding equals 以下几种情况不需要你override这个类的equals方法:这个类的每一个实例天生就是unique的,比如Thread:这个类的父类已经override了equals,并已经足够:这是个private或者package的class,你确定equals永远不会被调用,保险起见这时候你其实可以overrid…

Tips <Effective Java, Third Edition>一书英文版已经出版,这本书的第二版想必很多人都读过,号称Java四大名著之一,不过第二版2009年出版,到现在已经将近8年的时间,但随着Java 6,7,8,甚至9的发布,Java语言发生了深刻的变化. 在这里第一时间翻译成中文版.供大家学习分享之用. 11. 重写equals方法时同时也要重写hashcode方法 在每个类中,在重写 equals 方法的时侯,一定要重写 hashcode 方法.如果不这样做,你的类违反了…