In Kotlin data classes equality check, arrays, just like other classes, are compared using equals(…), which compares the arrays references, not the content. This behavior is described here: So, whenever you say arr1 == arr2 DataClass(arr1) == DataClass(arr2) … you get the arrays compared through equals(), i.e. referentially. Given that, val arr1 = intArrayOf(1, 2, … Read more
Because you are using the == (similarity) operator and PHP is coercing the string to an int. To resolve it use the === (equality) operator, which checks not only if the value is the same, but also if the data type is the same, so “123” string and 123 int won’t be considered equal.
== compares object references, it checks to see if the two operands point to the same object (not equivalent objects, the same object). If you want to compare strings (to see if they contain the same characters), you need to compare the strings using equals. In your case, if two instances of MyClass really are … Read more
is checks that 2 arguments refer to the same object, == checks that 2 arguments have the same value. dir() returns a list which contains the same data for both foo and 10, but the actual list instances for the 2 things are different.
Because “true” is converted to NaN, while true is converted to 1. So they differ. Like you reported, both are converted to numbers, because at least true can be (see Erik Reppen’s comment), and then compared.
With Java 7 you can now directly do a null safe equals: Objects.equals(x, y) (The Jakarta Commons library ObjectUtils.equals() has become obsolete with Java 7)
Unitils has this functionality: Equality assertion through reflection, with different options like ignoring Java default/null values and ignoring order of collections
Hibernate has a nice and long description of when / how to override equals() / hashCode() in documentation The gist of it is you only need to worry about it if your entity will be part of a Set or if you’re going to be detaching / attaching its instances. The latter is not that … Read more
Yes, the default implementation is Object’s (generally speaking; if you inherit from a class that redefined equals and/or hashCode, then you’ll use that implementation instead). From the documentation: equals The equals method for class Object implements the most discriminating possible equivalence relation on objects; that is, for any non-null reference values x and y, this … Read more
A difference is that “foo”.equals((String)null) returns false while “foo”.compareTo((String)null) == 0 throws a NullPointerException. So they are not always interchangeable even for Strings.