Your real question seem to be: Why: null >= 0; // true But: null == 0; // false What really happens is that the Greater-than-or-equal Operator (>=), performs type coercion (ToPrimitive), with a hint type of Number, actually all the relational operators have this behavior. null is treated in a special way by the Equals … Read more
It turns out Microsoft already has this covered in its testing framework: CollectionAssert.AreEquivalent Remarks Two collections are equivalent if they have the same elements in the same quantity, but in any order. Elements are equal if their values are equal, not if they refer to the same object. Using reflector, I modified the code behind … Read more
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 … Read more
You can simply check whether the multisets with the elements of x and y are equal: import collections collections.Counter(x) == collections.Counter(y) This requires the elements to be hashable; runtime will be in O(n), where n is the size of the lists. If the elements are also unique, you can also convert to sets (same asymptotic … Read more
Try [myObject class] for returning the class of an object. You can make exact comparisons with: if ([myObject class] == [MyClass class]) but not by using directly MyClass identifier. Similarily, you can find if the object is of a subclass of your class with: if ([myObject isKindOfClass:[AnObject class]]) as suggested by Jon Skeet and zoul.
the correct way to test floats for ‘equality’ is: if(Math.abs(sectionID – currentSectionID) < epsilon) where epsilon is a very small number like 0.00000001, depending on the desired precision.
Using dis to look at the bytecode generated for the two versions: not == 4 0 LOAD_FAST 0 (foo) 3 LOAD_FAST 1 (bar) 6 COMPARE_OP 2 (==) 9 UNARY_NOT 10 RETURN_VALUE != 4 0 LOAD_FAST 0 (foo) 3 LOAD_FAST 1 (bar) 6 COMPARE_OP 3 (!=) 9 RETURN_VALUE The latter has fewer operations, and is therefore … Read more
== is a binary equality operator. The left-hand operand of a binary operator appears to be fully evaluated before any part of the right-hand operand is evaluated. Java 11 Specification > Evaluation Order > Evaluate Left-Hand Operand First
The main reason is performance. When generics were introduced in .NET 2.0 they were able to add a bunch of neat classes such as List<T>, Dictionary<K,V>, HashSet<T>, etc. These structures make heavy use of GetHashCode and Equals. But for value types this required boxing. IEquatable<T> lets a structure implement a strongly typed Equals method so … Read more
array1.equals(array2) is the same as array1 == array2, i.e. is it the same array. As @alf points out it’s not what most people expect. Arrays.equals(array1, array2) compares the contents of the arrays. Similarly array.toString() may not be very useful and you need to use Arrays.toString(array).