C#

public class Foo : IEquatable<Foo>
{
    public static bool operator !=(Foo foo1, Foo foo2)
    {
        return !Equals(foo1, foo2); //under the hood, this STATIC, note STATIC method makes a call to the
                                    // INSTANCE-level Equals(object obj) method.
    }

    public static bool operator ==(Foo foo1, Foo foo2)
    {
        return Equals(foo1, foo2); //under the hood, this STATIC, note STATIC method makes a call to the
                                    // INSTANCE-level Equals(object obj) method.
    }

    public bool Equals(Foo foo)
    {
        if (foo == null) return false;
        return y == foo.y && x == foo.x;
    }

    public override bool Equals(object obj) //called by the static object.Equals(obj, obj) method
    {
        if (ReferenceEquals(this, obj)) return true;  
                                                     
        return Equals(obj as Foo);
    }

    public override int GetHashCode()
    {
        return y + 29*x;
    }

    private int y;
    private int x;
}