This article was originally posted by Javin Paul at Javarevisited.
Unlike C++ java doesn't provide freedom to programmer to overload the standard arithmetic operators e.g. +, -, * and /, Java has left lot of feature supported in C++ e.g. Java doesn't support multiple inheritance, no pointers in Java and no pass by reference in java. Rarely this question asked in interview to check how programmer thinks about certain features which java doesn't have. Though I don't know the real reason behind it I think following observation make sense on why Operator overloading is not supported in Java.
1) Simplicity and Cleanliness
Simple and clear design is one of the goals of java designer they just don't want to replicate the language but wanted to have a clear, truly object oriented language. Adding Operator overloading will definitely make design more complex than without it and it also slows the JVM because it needs to do extra work to identify the actual meaning of operators and reduce the opportunity to optimize the language by guarantee behavior of operators in Java.
2) Avoid programming errors
Java doesn't allow user defined operator overloading because if you allow programmer to do operator overloading they will come up with multiple meanings for same operator which will make the learning curve of any developer hard and things more confusing and messing. Its been observed that there is increase in programming errors when language supports operator overloading which in turn increase the development and delivery time and since Java and JVM has taken most of developers responsibility in memory management by proving garbage collector it doesn't really make sense to left this feature to pollute the code and a loop hole for programming errors.
3) JVM complexity
Form JVM perspective supporting operator overloading is more difficult and if the same thing can be achieved by using method overloading in more intuitive and clean way it does make sense to not support operator overloading in java. a complex JVM will result in slower JVM than a relatively simpler JVM and reduce the opportunity of optimization by taking out guaranteed behavior of operators in java.
4) Easy development of tools
This you can think of an additional benefit of not supporting operator overloading in Java.omission of operator overloading has kept the language easier to handle and process which in turn makes to developed the tools that process the language e.g. IDE or re-factoring tool. Re-factoring tools are far better than C++.
In conclusion many things which can be achieved via operator overloading can be achieved using method overloading using more intuitive and easy way and that might be the reason java designer thought that supporting operator overloading will not be a big benefit for language, but in fact only java designer can answer real motivation of why Java doesn't support operator overloading, like some other questions as Why Java doesn't support multiple inheritance or Why String is immutable in Java.
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