equals

scala> List(1,2,3) == List(1,2,3) res2: Boolean = true scala> Map(1 -> "Olle") == Map(1 -> "Olle") res3: Boolean = true But when trying to do the same with Array, it does not work the same. Why? scala> Array('a','b') == Array('a','b') res4: Boolean = false I have used 2.8.0.RC7 and 2.8.0.Beta1-prerelease. Because the definition of "equals" for Arrays is that they refer to the same array. This is consistent with Java's array equality, using Object.Equals , so it compares references. If you want to check pairwise elements, then use sameElements Array('a','b').sameElements(Array('a','b')) or

I have two object arrays like so: Object[] array1 = {0, 1, 2, 3}; Object[] array2 = {0, 1, 2, 3}; I would like to know if the arrays are equal. I'm defining equal as every value in array1 is the same as the value in that position in the array2. So these two arrays would be equal. What is the best why to find out if these two arrays are equal? if(array1 == array2) is not a deep equals so that won't work and I don't know if looping over each element and comparing them is the best and most efficient way to solve this problem. Does anyone have any better suggestions? Edit: I needed an equals that

If I implement java.lang.Comparable for a class, do I still have to override the equals() method? Or will the Comparable work for equals as well? If the answer is no , then what if some discrepancy arises? Let's say the way I term two objects as equal within the equals() method is different from the way I term two objects of the same class as equal within the compareTo() of the Comparable . Moreover, if I implement Comparable , do I also have to override equals() ? While it is recommended (and pretty sensible) that having a.compareTo(b) == 0 imply that a.equals(b) (and visa versa), it is not

I have some Java code which I'm translating to Scala. The code consists of some immutable classes which would fit the purpose of a case class in Scala. But I don't want to introduce bugs, therefore I want to be sure that the code being generated for equals and hashCode is/behaves equivalent to the current implementation. I already looked in "Programming in Scala" but it only says Third, the compiler adds “natural” implementations of methods toString, hashCode, and equals to your class. Scala has a compiler option -Xprint:typer , which you can use to get the "post-typing source code that it

Consider the following snippet: import java.util.*; public class EqualsOverload { public static void main(String[] args) { class Thing { final int x; Thing(int x) { this.x = x; } public int hashCode() { return x; } public boolean equals(Thing other) { return this.x == other.x; } } List<Thing> myThings = Arrays.asList(new Thing(42)); System.out.println(myThings.contains(new Thing(42))); // prints "false" } } Note that contains returns false !!! We seems to have lost our things!! The bug, of course, is the fact that we've accidentally overloaded , instead of overridden , Object.equals(Object) .

XML document: <doc> <A> <Node>Hello!</Node> </A> <B> <Node/> </B> <C> </C> <D/> </doc> How would you evaluate the following XPath queries? /doc/A/Node != 'abcd' /doc/B/Node != 'abcd' /doc/C/Node != 'abcd' /doc/D/Node != 'abcd' I would expect ALL of these to evaluate to true . However, here are the results: /doc/A/Node != 'abcd' true /doc/B/Node != 'abcd' true /doc/C/Node != 'abcd' false /doc/D/Node != 'abcd' false Is this expected behavior? Or is it a bug with my XPath provider (jaxen)? Recommendation : Never use the != operator to compare inequality where one or both arguments are node-sets.