Why doesn't Java need Operator Overloading? [closed]
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Improve this questionWhy doesn't Java need operator overloading? Is there any way it can be supported in Java?
Java only allows arithmetic operations on elementary numeric types. It's a mixed blessing, because although it's convenient to define operators on other types (like complex numbers, vectors etc), there are always implementation-dependent idiosyncrasies. So operators don't always do what you expect them to do. By avoiding operator overloading, it's more transparent which function is called when. A wise design move in some people's eyes.
Java doesn't "need" operator overloading, because no language needs it.
a + b is just "syntactic sugar" for a.Add(b) (actually, some would argue that a.Add(b) is just syntactic sugar for Add(a,b))
This related question might help. In short, operator overloading was intentionally avoided when Java was designed because of issues with overloading in C++.
Scala, a newer JVM language, has a syntax that allows method overloading that functions very much like operator overloading, without the limitations of C++ operator overloading. In Scala, it's possible to define a method named +, for example. It's also possible to omit the . operator and parentheses in method calls:
case class A(value: Int) {
def +(other: A) = new A(value + other.value)
}
scala> new A(1) + new A(3)
res0: A = A(4)
No language needs operator overloading. Some believe that Java would benefit from adding it, but its omission has been publicized as a benefit for so long that adding it is almost certainly politically unacceptable (and it's only since the Oracle buyout that I'd even include the "almost").
The counterpoint generally consists of postulating some meaningless (or even counterintuitive) overload, such as adding together two employees or overloading '+' to do division. While operator overloading in such languages as C++ would allow this, lack of operator overloading in Java does little to prevent or even mitigate the problem. someEmployee.Add(anotherEmployee) is no improvement over someEmployee + anotherEmployee. Likewise, if myLargeInteger.Add(anotherLargeInteger) actually does division instead of addition. At least to me, this line of argument appears thoroughly unconvincing at best.
There is, however, another respect in which omitting operator overloading does (almost certainly) have a real benefit. Its omission keeps the language easier to process, which makes it much easier (and quicker) to develop tools that process the language. Just for an obvious example, refactoring tools for Java are much more numerous and comprehensive than for C++. I doubt that this can or should be credited specifically and solely to support for operator overloading in C++ and its omission in Java. Nonetheless, the general attitude of keeping Java simple (including omission of operator overloading) is undoubtedly a major contributing factor.
The possibility of simplifying parsing by requiring spaces between identifiers and operators (e.g., a+b prohibited, but a + b allowed) has been raised. At least in my opinion, this is unlikely to make any real difference in most cases. The reason is fairly simple: at least in a typical compiler, the parser is preceded by a lexer. The lexer extracts tokens from the input stream and feeds them to the parser. With such a structure, the parser wouldn't see any difference at all between the a+b and a + b. Either way, it would receive exactly three tokens: identifer, +, and identifier.
Requiring the spaces might simplify the lexer a tiny bit--but to the extent it did, it would be completely independent of operator overloading, at least assuming the operator overloading was done like it is in C++, where only existing tokens are used1.
So, if that's not the problem, what is? The problem with operator overloading is that you can't hard-code a parser to know the meaning of an operator. With Java, for some given a = b + c, there are exactly two possibilities: a, b and c are each chosen from a small, limited set of types, and the meaning of that + is baked into the language, or else you have an error. So, a tool that needs to look at b + c and make sense of it can do a very minimal parse to assure that b and c are of types that can be added. If they are, it knows what the addition means, what kind of result it produces, and so on. If they are't, it can underline it in red squiggles (or whatever) to indicate an error.
For C++, things are quite different. For an expression like a = b + c;, b and c could be of almost entirely arbitrary types. The + could be implemented as a member function of b's type, or it could be a free function. In some cases, we might have a number of operator overloads (some of which could be templates) that could carry out that operation, so we need to do overload resolution to determine which one the compiler would actually select based on the types of the parameters (and if some of them are templates, the overload resolution rules get even more complex).
That lets us determine the type of the result from b + c. From there we basically repeat the whole process again to figure out what (if any) overload is used to assign that result to a. It might be built-in, or it might be another operator overload, and there might be multiple possible overloads that could do the job, so we have to do overload resolution again to figure out the right operator to use here.
In short, just figuring out what a = b + c; means in C++ requires nearly an entire compiler front-end. We can do the same in Java with a much smaller subset of a compiler2
- I suppose things could be somewhat different if you allowed operator overloading like, for example, ML does, where a more or less arbitrary token can be designated as an operator, and that operator can be given a more or less arbitrary associativity and/or precedence. I believe ML handles this entirely in parsing, not lexing, but if you took this basic concept enough further, I can believe it might start to affect lexing, not just parsing.
- Not to mention that most Java tools will use the JDK, which has a complete Java compiler built into the JVM, so tools can normally do most such analysis without dealing directly with parsing and such at all.
java-oo compiler plugin can add Operator Overloading support in Java.
It's not that java doesn't "need" operator overloading, it's just a choice made by its creators who wanted to keep the language more simple.
Java does not support operator overloading by programmers. This is not the same as stating that Java does not need operator overloading.
Operator overloading is syntactic sugar to express an operation using (arithmetic) symbols. For obvious reasons, the designers of the Java programming language chose to omit support for operator overloading in the language. This declaration can be found in the Java Language Environment whitepaper:
There are no means provided by which programmers can overload the standard arithmetic operators. Once again, the effects of operator overloading can be just as easily achieved by declaring a class, appropriate instance variables, and appropriate methods to manipulate those variables. Eliminating operator overloading leads to great simplification of code.
In my personal opinion, that is a wise decision. Consider the following piece of code:
String b = "b";
String c = "c";
String a = b + c;
Now, it is fairly evident that b and c are concatenated to yield a. But when one consider the following snippet written using a hypothetical language that supports operator overloading, it is fairly evident that using operator overloading does not make for readable code.
Person b = new Person("B");
Person c = new Person("C");
Person a = b + c;
In order to understand the result of the above operation, one must view the implementation of the overloaded addition operator for the Person class. Surely, that makes for a tedious debugging session, and the code is better implemented as:
Person b = new Person("B");
Person c = new Person("C");
Person a = b.copyAttributesFrom(c);
OK Well... we have a very discussed and common issue. Today, in software industry, there are, mainly, two different types of languages:
- Low level languages
- High level languages
This distinction was useful about 10 years before now, the situation, at present, is a bit different. Today we talk about business-ready applications. Business models are some particular models where programs need to meet many requirements. They are so complex and so strict that coding an application with a language like c or c++ would be very time-spending. For this reason hybrid languages where invented.
We commonly know two types of languages:
- Compiled
- Interpreted
Well, today there is another one:
- Compiled/Interpreted: in one word: MANAGED.
Managed languages are languages that are compiled in order to produce another code, different from the original one, but much more complex to handle. This INTERMEDIATE LANGUAGE is then INTERPETED by a program that runs the final program.
It is the common dynamics we came knowing from Java... It is a winning approach for business-ready applications. Well, now going to your question...
Operator overloading is a matter that concerns also multiple inheritance and other advanced characteristics of low level languages. Java, as well as C#, Python and so on, is a managed language, made to be easy to write and useful for building complex applications in very few time. If we included operator overloading in Java, the language would become more complex and difficult to handle.
If you program in C++ you sure understand that operator overloading is a very very very delicate matter because it can lead to very complex situations and sometimes compiler might refuse to compile because of conflicts and so on... Introducing operator overloading is to be done carefully. IT IS POWERFUL, but we pay this power with an incredibly big load of problems to handle.
OKOK IT IS TRUE, you might tell me: "HEY, But C# uses operator overloading... What the hell are you telling me? why c# supports them and Java not?". Well, this is the answer. C#, yes, implements operator overloading, but it is not like C++. There are many operator that cannot be overloaded in c# like "new" or many others that you can overload in c++... So C# supports operator overloading, but in a much lower level than c++ or other languages that fully supports it. But this is not a good answer to the earlier question... The real answer is that C# is more complex than Java. This is a pro but also a con. It is a matter of deciding where to place the language: high level, higher level, very high level? Well, Java does not support op overloading because it wants to be fast and easy to manage and use. When introducing op overloading, a language must also carry a large amount of problems caused by this new functionality.
It is exactly like questioning: "Why does Java not support multiple inheritance?" Because it is tremendously complex to manage. Think about it... IT WOULD BE IMPOSSIBLE for a managed language to support multiple inheritance... No common class tree, no object class as a common base class for all classes, no possibility of upcasting (safely) and many problems to handle, manage, foresee, keep in count...
Java wants to be simple. Even if I believe that future implementations of this language will result in supporting op overloading, you will see that the overloading dynamics will involve a fewer set of all the possibilities you have about overloading in C++.
Many others, here, also told you that overloading is useless. Well I belong to those ones who think this is not true. Well, if you think this way (op overloading is useless), then also many other features of managed languages are useless too. Think about interfaces, classes and so on, you really do not need them. You can use abstract classes for interface implementations... Let's look at c#... so many sugar syntax, LINQ and so on, they are not really necessary, BUT THEY FASTEN YOUR WORK... Well, in managed languages everything that fasten a development process is welcome and does not imply uselessness. If you think that such features are not useful than the entire language itself would be useless and we all would come back programming complex applications in c++, ada, etc. The added value of managed languages is to be measured right on this elements.
Op overloading is a very useful feature, it could be implemented in languages like Java, and this would change the language structure and purposes, it would be a good thing but a bad thing too, just a matter of tastes. But today, Java is simpler than C# even for this reason, because Java does not supports op overloading.
I know, maybe I was a little long, but hope it helps. Bye
Check Java Features Removed from C and C++ p 2.2.7 No More Operator Overloading.
There are no means provided by which programmers can overload the standard arithmetic operators. Once again, the effects of operator overloading can be just as easily achieved by declaring a class, appropriate instance variables, and appropriate methods to manipulate those variables. Eliminating operator overloading leads to great simplification of code.
Java doesn't support operator overloading (one reference is the Wikipedia Operator Overloading page). This was a design decision by Java's creators to avoid perceived problems seen with operator overloading in other languages (especially C++).
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