String s = “”; String s2 = someUserInputVariale.toLowercase(); // where the user entered in “” Something like that would cause s == s2 to evaluate to false. Lots of code sill create new Strings without exposing the call to new String().
This should work exactly as you expect it to. In lua ‘==’ for string will return true if contents of the strings are equal. As it was pointed out in the comments, lua strings are interned, which means that any two strings that have the same value are actually the same string.
Why reinvent the wheel? Give Lodash a try. It has a number of must-have functions such as isEqual(). _.isEqual(object, other); It will brute force check each key value – just like the other examples on this page – using ECMAScript 5 and native optimizations if they’re available in the browser. Note: Previously this answer recommended Underscore.js, … Read more
Whether you should do this depends on the semantics of your class. That is, what does it mean to say that two objects of your class are equivalent? The most important distinction is between objects with value semantics and objects with entity semantics. Entity objects are not equivalent even if they have equivalent attributes (colour, … Read more
There’s a free 1st edition of PinS that discuss this subject just as well. However, I think the best source is this article by Odersky discussing equality in Java. The discussion in PinS is, iirc, an abbreviated version of this article.
This is because your equals() is not symmetric: new Foo(“ID1”).equals(“ID1”); but “ID1”.equals(new Foo(“ID1”)); is not true. This violates the equals() contract: The equals method implements an equivalence relation on non-null object references: […] It is symmetric: for any non-null reference values x and y, x.equals(y) should return true if and only if y.equals(x) returns true. … Read more
You can not overload the == operator, but you can override equals(Object) if you want it to behave differently from the == operator, i.e. not compare references but actually compare the objects (e.g. using all or some of their fields). Also, if you do override equals(Object), have a look at hashCode() as well. These two … Read more
I found that NOT (NULL <=> 1) works and I think it is also ISO standard compliant, but is cumbersome. A better way to show using column names would be like this: NOT (tbl.col1 <=> 1)
It works for you because your code does not use any functionality (HashMap, HashTable) which needs the hashCode() API. However, you don’t know whether your class (presumably not written as a one-off) will be later called in a code that does indeed use its objects as hash key, in which case things will be affected. … Read more
Recommendation: Never use the != operator to compare inequality where one or both arguments are node-sets. By definition the expression: $node-set != $value evaluates to true() exactly when there is at least one node in $node-set such that its string value is not equal to the string value of $value. Using this definition: $empty-nodeset != … Read more