Java vs Clojure

• A Hello world needs package, class, static method and the actual printf.
• Reading a line from input requires instatiating 5 objects in the right order.
• Exceptions are everywhere, particularly since all values are nullable.
• Java has a getter/setter culture, but without native syntax support.
• portable Java code lacks anonymous functions, and continues to lack good support for partial application, compensating instead with verbose design patterns, kludges like anonymous inner classes, or just inline code.
• It is statically typed without type inference, with a culture that promotes long class names.
• Poor support for sum-types and pattern matching leads to overuse of inheritance for dynamic dispatch and chains of nested conditionals

Especially for beginners, this can make reading Java code feel overwhelming; most Java courses tell students to simply copy, paste, and ignore a significant percentage of the code until they've learned enough to understand what it means.

For experienced programmers, this makes Java feel tedious, especially without an IDE, and actively discourages some solutions and some forms of abstraction.

Some features in Java can be quite confusing for beginners.

Encapsulation is needlessly obfuscated with a confusing access control model. As an example, the "protected" keyword not only grants access to child classes, but to the entire package. Since small programs are written as one package, it becomes functionally equivalent to "public".

In OOP, everything is supposed to be an object, but, in Java, primitive types such as integers, booleans and characters are not, and must be handled as special cases.

Java continues to lack many high-level features, and, particularly prior to Java 7, compensated by adding confusing Java-only features, such as anonymous subclasses. Some example code is unreadable without knowing a special-case feature, libraries differ in style based on when they were released or what platform they target(e.g., Android vs. Desktop), and some solutions just aren't available on some platforms.

Overly focuses on class-based OOP to the detriment of programmer freedom or alternative paradigms that are better for various problems. Traps programmers into an always use class-based OOP mindset.

Type erasure means it doesn't even exist at runtime. The whole generics system is confusing for beginners.

Too far from the machine hardware.

I've been developing in Java for 20 years and I love this language, I've never used a better designed one over the last 30+ years. However, starting with version 6, the number of really useful features in each release has steadily decreased. There is now too much marketing in Java's evolution and too few concern about developers' needs (the functionalities of the applications we develop haven't changed and enterprise application architecture is much simpler than 20 years ago). I'm deeply sad to say that today, learning Python is a much wiser choice.

Java is a garbage collected language and it does not force programmers to think about memory allocation and management for their programs. This is fine most of the time. However, it may cause some difficulties in adjusting to a non-GC language (such as C for example), where memory management needs to be done manually. But if good coding practices and habits are followed, this shouldn't be much of a problem.

It's just barely good enough to make decent IDEs, but it's not at the level of Idris or even Haskell. For large enterprise projects, the IDE support is important, but the static typing in Java just gets in the way for the smaller projects beginners would start with.

Python is duck typed and this makes small programs easy to develop quickly, but the price is that you have to write unit tests to avoid breaking larger programs. In contrast, you can be reasonably certain that a program that actually compiles in Idris does what you want, because assertions are built into the powerful type system. Java can't make that claim and still requires unit tests. Java has the worst of both worlds because of its poor static type system.

The type system gets in your way more than it helps. Heavy IDE support is absolutely required for reasonable productivity. This means beginners have to learn not just the language, but eventually a complex, heavyweight IDE too.

Java evolves very slowly - lambda expressions weren't available until Java 8 (which is not available on Android), and despite getters/setters being a long-time convention, the language still doesn't have native accessor syntax (a la C#'s properties). It's unlikely newer, popular features like list comprehensions or disjoint union types will be available anytime soon. While not strictly required for novice programmers, these make problems more complicated and tedious than they need to be - for example, when a simple local function would do, (portable) Java demands anonymous inner classes, an interface and a class, or worse, no abstraction at all.

Since C# came later, it could avoid the blatant mistakes made in Java.

Java utilizes principles that primarily organize code into "classes" as the central concept, instead of more familiar organizational methods.

Checked exceptions add significantly to the cognitive load of the beginner. The more rules unrelated to the actual task that you pile onto the beginner, the slower he gets. Exponentially. And for what? Sure, they look good on paper, but checked exceptions are useless in the real world. They don't scale.

When you're calling APIs five levels deep and your method's throws clause balloons to 80 exceptions you might see, it gets kind of ridiculous. So you just say throws Exception, which defeats the whole feature, but is more pointless boilerplate in an already tediously verbose language.

Or worse, while developing you can't be bothered and just catch{} and silently swallow them all. Then you forget about it. Now you don't even have exceptions. The cure is worse than the disease!

So the wiser Java programmers will wrap all checked exceptions into a runtime exception, effectively making exceptions unchecked. That's at the cost of more boilerplate, but it's the lesser of evils. Unfortunately, Java doesn't even have macros to do this part for you. Maybe your IDE can write code templates for you, but that doesn't make it any easier to read.

Clojure's error messages more often than not are very confusing. They usually involve stack traces that do not thoroughly explain where the error was caused or what caused it.

Tendency to devolve into difficult to manage mess of styles. Not recommended for professional use.

Way too niche and in-group behavior, while trying to trash other languages. Only pays for select few, who run the "game" on others.

Some language constructs were obviously created as workarounds for JVM limitations. This makes the language much less elegant than it could have been.
Also, the JVM has a very cumbersome FFI.

Perhaps some may consider this attribute an advantage, but I do not. Clojure does not attempt to maintain significant compatibility with other Lisps. So, if you already know a Lisp or are used to the way Lisp works in general, you'll probably be confused if you take a look at Clojure. See these resources for more details on this subject:

• https://clojure.org/reference/lisps
• http://stackoverflow.com/q/6008313/2636454
• http://gilesbowkett.blogspot.com/2015/01/one-major-difference-between-clojure.html
• http://softwareengineering.stackexchange.com/q/153128/166211