equals | 易学教程

C# Assert.AreNotEqual versus Equals

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问题 While trying to verify to myself, that C# Equals for IEnumerables is a reference equals, I found something odd. With the following setup in NUnit var a = (IEnumerable<string>)(new[] { "one", "two" }); var b = (IEnumerable<string>)(new[] { "one", "two" }); this test Assert.IsFalse(a.Equals(b)); passes, while this test Assert.AreNotEqual(a, b); doesn't. Can anybody explain why? Edit: Thanks for the answers. I just read the documentation for NUnit, and it says the same thing, that AreEqual and

how does default equals implementation in java works for String? [duplicate]

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问题 This question already has answers here : Demonstrating string comparison with Java (3 answers) Closed 6 years ago . We all know if we create two String objects and use == to compare them it will return false and if we use equals to method it will return true. But by default equals method implement == only , then how does it return true , it should return whatever == is returning ?? 回答1: Yes by default equals method implements == in Object class . But you can Override the equals method in your

How to implement equals() and hashcode() methods in BaseEntity of JPA?

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问题 I have a BaseEntity class which is a superclass of all JPA entities in my application. @MappedSuperclass public abstract class BaseEntity implements Serializable { private static final long serialVersionUID = -3307436748176180347L; @Id @GeneratedValue(strategy = GenerationType.IDENTITY) @Column(name = "ID", nullable=false, updatable=false) protected long id; @Version @Column(name="VERSION", nullable=false, updatable=false, unique=false) protected long version; } Every JPA entity extends from

How to give all divs same amount of space on each side

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问题 Hello I've got a question about a layout. I have a website where I fill divs with information. These Divs need to be next to each other with the same amount of space between them and between the sides of the container div. I'm making it for mobile phones so I don't know the width of there screens and it should look fine on all the different screen resolutions. Currently I've got this: Fiddle: Fiddle HTML: <div id="container"> <div id="lineout"> <div id="foto"><img src="img/logo_null_image.jpg

Compare two strings regardless of case size in perl

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问题 is there anyway to compare two strings regardless of case size? For Example "steve" eq "STevE" <----- these would match "SHOE" eq "shoe" You get the picture 回答1: yes - use uc() (upper-case function; see http://perldoc.perl.org/functions/uc.html ) $ perl -e 'print uc("steve") eq uc("STevE"); print "\n";' 1 $ perl -e 'print uc("SHOE") eq uc("shoe"); print "\n";' 1 $ perl5.8 -e 'print uc("SHOE") eq uc("shoe1"); print "\n";' $ You can obviously use lc() as well. If you want the actual "eq"

How does Scala's equals method work in the case of a List?

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问题 list1 == list2 To do the above check, will Scala iterate through both lists and call equals on each pair of elements ? (I am sure, this question has been asked before, but I could not find a good answer with Google & Co) 回答1: You can find this out yourself for any method by looking at the Scaladoc and finding out where it's defined, and then looking at the source. If you start with the online docs, you can do this all just with clicking: go to the method, open it up by clicking on the arrow

Deep Comparision of Two Java Objects

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问题 Already referred few question here and there. Use Case - 1.) Given any Two objects , compare both of them property by property. 2.) It will contains Collections also, now compare collections of both the objects, now inside collection same data can be upside down, meaning say i have List<Address> , it contains two entries in both (say Residential Address , Office Address ), but in both list the data may be at different indexes. 3.) Need to create 3rd Object of same type, with similar data

浅谈equals和hashcode

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转自：http://www.sunxin.org/forum/thread/19720.html 先谈equals。 equals是Object类提供的方法之一，众所周知，每一个java类都继承自Object类，所以说每一个对象都有equals这个方法。而我们在用这个方法时却一般都重写这个方法，why? Ok，先看一个Object类中equals()方法的源代码： public boolean equals(Object obj) { return (this == obj); } 从这个方法中可以看出，只有当一个实例等于它本身的时候，equals()才会返回true值。通俗地说，此时比较的是两个引用是否指向内存中的同一个对象，也可以称做是否实例相等。而我们在使用equals()来比较两个指向值对象的引用的时候，往往希望知道它们逻辑上是否相等，而不是它们是否指向同一个对象——这就是我们通常重写这个方法的原因。在程序员之家论坛中有这样一篇文章《全面理解Java中的String数据类型》(链接http://www.phome.asia/forum/thread/19667.html) ，在这篇文章中,String s1 = new String(“kvill”),String s2 = new String(“kvill”); s1.equals(s2)为ture

【转】hashcode()与equals()

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源地址： http://lxj8495138.iteye.com/blog/286024 java.lnag.Object中对hashCode的约定：在一个应用程序执行期间，如果一个对象的equals方法做比较所用到的信息没有被修改的话，则对该对象调用hashCode方法多次，它必须始终如一地返回同一个整数。如果两个对象根据equals(Object o)方法是相等的，则调用这两个对象中任一对象的hashCode方法必须产生相同的整数结果。如果两个对象根据equals(Object o)方法是不相等的，则调用这两个对象中任一个对象的hashCode方法，不要求产生不同的整数结果。但如果能不同，则可能提高散列表的性能。来源： oschina 链接： https://my.oschina.net/u/192322/blog/53244

Single Equals in MYSQL

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问题 I was wondering why MYSQL uses a single equals sign in conditional statements instead of the more typical two equals signs. Is there a technical/historical reason for this? Thanks. 回答1: Hi, I was wondering why MYSQL uses a single equals sign in conditional statements instead of the more typical two equals signs. Is there a technical/historical reason for this? Thanks. Comparison is much more common in SQL than assignment. That's why SQL uses more short syntax to do more common things. In