Is it possible to create a custom operator in Java?

Question

Similar to Is it possible to create a new operator in c#?, is it possible to create your own operator for Java? I would initially say no since you can't overload, but then again, String supports + and += (implicitly through StringBuilder at execution time etc).

Solution 1

Java doesn't allow for this.

However, if you want to achieve this sort of syntax whilst being able to run your code on a JVM (and with other Java code), you could look at Groovy, which has operator overloading (and with which you could also use DSLs for short syntax which would have similar effects to using custom operators).

Note that defining custom operators (not just overloading) is a big deal in any language, since you would have to be able to alter the lexer and grammar somehow.

Solution 2

No, Java is not extensible in this way. You can't add operators, and you can't even further overload built-in operators like + - even standard library classes like BigInteger have to use methods such as add() rather than operators such as +.

Scala (another static JVM language) gets around this by using method calls rather than built-in operators, and allowing any characters in method names, so you can define new methods that appear to be operators, i.e.

a + 1

is syntactic sugar for:

a.+(1)

Comments

[ahodder]

I'm not asking to overload. I'm asking to create a new symbol.

[Kevin Welker]

in your question, you used both terms "new" and "overload" so it is a bit confusing.

[Bruno]

That article was visibly written by someone who hasn't done any numerical code in Java. Being able to multiply matrices with operator overloading with NumPy in Python (for example) is very handy for readability compared with having to call the likes of RealMatrix.multiply(RealMatrix) everywhere.

[Louis Wasserman]

That said, Java not having operator overloading was a very deliberate decision -- you may find it best to avoid such things.

[Bruno]

@LouisWasserman: as I was saying in another comment, I understand the decision, but that doesn't make Java very suitable for math programming unfortunately. With matrices, a.multiply(b.multiply(c.add(d)).add(e)) isn't great... NumPy makes good usage of operator overloading in Python.

[ianpojman]

agreed... I haven't done much of it at all, and the Java language doesn't seem like the best choice for that. The Java platform is great for it though

[Aaron Franke]

Dead link? It doesn't load for me.

[David Buck]

While this link may answer the question, it is better to include the essential parts of the answer here and provide the link for reference. Link-only answers can become invalid if the linked page changes. - From Review

[Mark Rotteveel]

@DavidBuck the answer is "No. Java doesn't allow operator overloading.", the link just supports that claim. In other words, this is not a link-only answer.

[logbasex]

@DavidBuck, MarkRotteveel: I'm initially intended to write a comment but my reputation wasn't enough. Thank you for all kindness, I'll better at the next time as a contributor.