equality

I have the following code: object val1 = 1; object val2 = 1; bool result1 = (val1 == val2);//Equals false bool result2 = val1.Equals(val2); //Equals true What's up with that? Is the only way to fix this to go with .Equals() method? The operator == is static, not virtual, so the behaviour is determined by the static type and not the runtime type. The default implementation for == on objects of reference type is to compare the references (although types can implement a different behaviour, for example string ). You have two different objects and they don't have the same reference so == returns

Assuming: val l1 = List(1,2,3) val l2 = List(2,3,1) I want a method that confirms that l1 is equal to l2 (as in same contents but different order). Is there an API method on List/Seq to do this? l1.sameElements(l2) does not work as it verifies order as well. I've come up with the following: l1.foldLeft(l1.size == l2.size)(_ && l2.contains(_)) Is there anything more succinct than the above to do this comparison? If what you want is "these lists contain the same elements, irrespective of order or repetitions": l1.toSet == l2.toSet If what you want is "these lists contain the same elements, and

I have a piece of code that behaves differently depending on whether I go through a dictionary to get conversion factors or whether I use them directly. The following piece of code will print 1.0 == 1.0 -> False But if you replace factors[units_from] with 10.0 and factors[units_to ] with 1.0 / 2.54 it will print 1.0 == 1.0 -> True #!/usr/bin/env python base = 'cm' factors = { 'cm' : 1.0, 'mm' : 10.0, 'm' : 0.01, 'km' : 1.0e-5, 'in' : 1.0 / 2.54, 'ft' : 1.0 / 2.54 / 12.0, 'yd' : 1.0 / 2.54 / 12.0 / 3.0, 'mile' : 1.0 / 2.54 / 12.0 / 5280, 'lightyear' : 1.0 / 2.54 / 12.0 / 5280 / 5.87849981e12, }

What is the difference between the String#equals method and the String#contentEquals method? The String#equals() not only compares the String's contents, but also checks if the other object is also an instance of a String . The String#contentEquals() only compares the contents (the character sequence) and does not check if the other object is also an instance of String . It can be anything as long as it is an implementation of CharSequence which covers a.o. String , StringBuilder , StringBuffer , CharBuffer , etc. To put it easily: String.contentEquals() is the smarter brother of String.equals

Say I have my own class public class MyObj { /* ... */ } It has some attributes and methods. It DOES NOT implement equals, DOES NOT implement hashCode. Once we call equals and hashCode, what are the default implementations? From Object class? And what are they? How the default equals will work? How the default hashCode will work and what will return? == will just check if they reference to the same object, so it's easy, but what about equals() and hashCode() methods? Etienne de Martel Yes, the default implementation is Object's (generally speaking; if you inherit from a class that redefined

I've encountered something which seems inconsistent on the part of the interpreter, though I know it probably makes sense and I just don't understand it. It has to do with evaluating the equality of a truthy/falsy values and Booleans. Example 1: if (document.getElementById('header')) { //run code here } If the element with an id of 'header' is found in the document, the condition is true because the presence of an object is considered truthy. Example 2: if (document.getElementById('header) == true) { // run code here } Presuppose the referenced element is found within the document. It was