Dot equals and the source keyword

A number of comments to yesterday's blog on a dot equals operator for overloading equals() objected to the syntax. As I tried to show, using the most logical syntax of == isn't possible in Java. Or is it?

Source keyword

Howard Lovatt has suggested using a source keyword to identify the version of the Java language that the source code is written in. This would appear before the package statement:

/**
 * Copyright...
 */
source 7;
package com.foo.bar;

public class Foo {
  // normal class stuff, but can use Java 7 syntax
}

The addition of this keyword could allow the radical change of redefining == to === and .equals() to == in Java 7 code. Files with 'source 7' would use the new equals operators, files with source 6 (or no source keyword) would use the old equals operators.

  source 6;  // keyword specifying Java version
  ...
  if (person.equals(input)) { ... }  // test by equals()
  if (person == input) { ... }       // test by equality

  source 7;  // keyword specifying Java version
  ...
  if (person == input) { ... }   // test by equals()
  if (person === input) { ... }  // test by equality

I'll be honest - this concept seems like a 'technically it would work but its a really bad idea' thing. Redefining == in Java, so it means two different things depending on what the source version is just bound to cause trouble. Thats why yesterday's blog is seeking a new operator to represent equals().

Anyway, I include this blog just to show what is possible with syntax change - not what I actually want.