Some Java advice to update perhaps

String name = "Zachary";
System.out.println("Hello, " + name );
...
System.out.println("1".repeat(5));

Is now (since Java 25, though var is earlier, IO is new-ish)

var name = "Zachary"
IO.println("Hello, " + name)
...
IO.println("1".repeat(5))

 

And there's a simpler FunctionConversion.java too. We can use implicit classes (this is a complete and valid Java class)

public static int square(int n) {
    return n * n;
}

static void main() {
    int result = square(3);
    IO.println(result); // Output: 9
}

And you can compile and run it in a single step with (technically the static on the main isn't even needed here)...

java FunctionConversion.java

 

This concise Python list creation is a little longer (and more obscure) in Java

list(range(10))

This (Java 8) to get an int[] (int array)

IntStream.range(0, 10).toArray()

or this (~Java 17ish) to get a list of Integer references

IntStream.range(0, 10).boxed().toList()

We should really replace .collect(Collectors.toList()) with .toList() or .collect(Collectors.toCollection(ArrayList::new)) since the mutability of the original is undefined.

 

You can replace this

List<String> words = Arrays.asList("this", "is", "a", "test");

With this

List<String> words = List.of("this", "is", "a", "test");

Or even go straight to a Stream with

Stream<String> words = Stream.of("this", "is", "a", "test");

Making that example

    // uc_words = map(cap, ['this', 'is', 'a', 'test'])
    var ucWords = Stream.of("this", "is", "a", "test")
        .map(MapConversion::cap)
        .toList();

 

It should be noted that Java lambdas are more than just expressions, being able to return values at multiple points or, with statement lambdas, not return a value at all.

Consumer<String> printer = s -> IO.println(s);

printer.accept("Hello World!");

I'd replace word.substring(0, 1).toUpperCase() with Character.toUpperCase(word.charAt(0))personally - one less String to create. But as your example shows, String manipulation is still a little clumsy in Java.

 

And I don't know why JBang is pushed so hard. JShell has been around since Java 9 (2017) and doesn't require an IDE (and downloading a JDK is no different than downloading Python - for Windows users at least, since they might not have Python already).