From apidoc, Float.compare: Compares the two specified float values. The sign of the integer value returned is the same as that of the integer that would be returned by the call: new Float(f1).compareTo(new Float(f2)) Float.compareTo: Compares two Float objects numerically. There are two ways in which comparisons performed by this method differ from those performed … Read more
Yes it is possible to do such a thing. (And people have done it.) But it won’t allow you to put your objects into a HashMap, HashSet, etc. That is because the standard collection classes expect the key objects themselves to provide the equals and hashCode methods. (That is the way they are designed to … 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.
There are several things going on. Firstly, in this example: string s1 = “a”; string s2 = “a”; Console.WriteLine(s1 == s2); You claim that: Both are different object reference. That’s not true due to string interning. s1 and s2 are references to the same object. The C# specification guarantees that – from section 2.4.4.5 of … Read more
in Eclipse right mouse click-> source -> generate hashCode() and equals() gives this: /* (non-Javadoc) * @see java.lang.Object#hashCode() */ @Override public int hashCode() { final int prime = 31; int result = 1; result = prime * result + (code == null ? 0 : code.hashCode()); return result; } /* (non-Javadoc) * @see java.lang.Object#equals(java.lang.Object) */ … Read more
Here’s a simple but realistic example of what can happen if a comparison method is inconsistent with equals. In the JDK, BigDecimal implements Comparable but its comparison method is inconsistent with equals. For example: > BigDecimal z = new BigDecimal(“0.0”) > BigDecimal zz = new BigDecimal(“0.00”) > z.compareTo(zz) 0 > z.equals(zz) false This is because … Read more
How does that work if the fields that it’s based on are mutable? It doesn’t in the sense that the hash code will change as the object changes. That is a problem for all of the reasons listed in the articles you read. Unfortunately this is the type of problem that typically only show up … Read more
Implementing IEquatable<T> for a Value Type Implementing IEquatable<T> for a value type is a little bit different than for a reference type. Let’s assume we have the Implement-Your-Own-Value-Type archetype, a Complex number struct. public struct Complex { public double RealPart { get; set; } public double ImaginaryPart { get; set; } } Our first step … Read more
IEqualityComparer<T> is an interface for an object that performs the comparison on two objects of the type T. IEquatable<T> is for an object of type T so that it can compare itself to another of the same type.
You really can’t compare floating point and integral values in a naive way; particularly, since there’s the classic floating point representation challenges. What you can do is subtract one from the other and see if the difference between them is less than some precision you care about, like so: int iValue = 0; double dValue … Read more