| Metrics | Scala | Java |
| When it started | 2004 | 1995 |
| Object Oriented/Functional | Hybrid.
Scala unites two worlds: object-oriented programming and functional programming. |
Object Oriented.
From Java 8, functional programming aspects like Lambda expression have been integrated into Java eco-system. |
| Learning Curve | Hard | Easier than Scala |
| Coding Style | Compact | Verbose |
| Performance | Though you can write compact codes in Scala, the performance is actually much slower when compared to Java. | Java is simple, super-fast and efficient in handling tasks |
| Compile Time | Much Slower than Java | Much Faster than Scala |
| Readability | Less | Better than Scala.
Although Java is too verbose, it is more readable than Scala. Why? Because Scala can get too nested at times. Imagine a function inside a function inside another, inside an object inside a class. Our brains aren’t calibrated to that less a level of abstraction. Java is nested too, but lesser than Scala. |
| IDEs (Integrated Development Environment) Support | The currently Scala supported IDEs are very less mature. | Java has a myriad of IDEs available to aid you with development. |
| Backward Compatibility | Not backward-compatible | Backward-compatible |
| Debugging | Debugging is very hard. | Java is much easier on the programmers with debugging. |
| Community | Community is younger and smaller. | Very large Community. |