Why doesn’t zsh autocomplete .java source files when using java MyFile.java?

Question

Since Java 10 as I recall, we can run Java source files directly from the command line:

bash

$ java Math.java

The JVM compiles and executes the file automatically.

However, in zsh, tab autocompletion with java does not list .java files—just .class, .jar, or other artifacts (perhaps .war and maybe others).

Minimal reproducible example:

Create a simple Java source file:

// Math.java
public class Math {
 public static void main(String[] args) {
 System.out.println("Hello from Math!");
 }
}

Open a zsh shell and try tab-completing after typing:

$ java [ press <TAB> ]

Only Math.class or Math.jar appear. Math.java doesn’t.

Questions:

• Is it possible to configure zsh (or its completion system) so .java files are autocompleted with java?

EDIT:

I tried to the what in his answer. However, no luck. First, I downloaded the updated _java file and I placed it where it was installed, ie.

❯ pacman -Ql zsh |grep java
zsh /usr/share/zsh/functions/Completion/Unix/_java
zsh /usr/share/zsh/functions/Completion/Unix/_java_class

I placed it under /usr/share/zsh/functions/Completion/Unix/_java, replacing the original file. Then I logged out and then logged it. It hasn't fixed the issue. PLease have a look at the following screenshot:

enter image description here

In ~/src I have a few *.java files:

❯ ls *.java
  NoNPE.java  OpenPortScanner.java 

I run oh-my-zsh. To test whether this causes issues, I run zsh in the following way: zsh -f so that no config file was loaded. It turns out that there seems to be autocomplete functionality for *.java files as know I see folders and *.java files being suggested. In other words, oh-my-zsh seems to be the problem. How can I fix that?

• Stéphane Chazelas: With zsh -f, you don't get the advanced completion. You still need to run at least autoload compinit; compinit.
• Gilles 'SO- stop being evil': Regarding your update: 1. Don't overwrite the distribution's files: they will be re-overwritten when the zsh package is upgraded. Instead, put the file in a directory listed by echo $fpath somewhere under your home directory. 2. When you change (as opposed to adding) a completion file, you need to arrange to regenerate the cache, see unix.stackexchange.com/questions/535509/… .

Answer 1

That's not what I observe. For me, java Tab offers Math (not Math.class) where there's a Math.class in the current working directory or $CLASSPATH, and Math.jar only on java -jar Tab.

It's true the _java completer from zsh 5.9, released in May 2022, the latest release as of writing, doesn't offer .java file completions to the java command. It was last modified in 2019 before java commands accepting .java files were common-place.

But the offering of .java files in completion of the java command was later added in February 2024 so will be available in the next release of zsh.

To get it in older releases, you can always pull the _java completer from the development version and add it to a directory in your $fpath (or replace the one from the zsh installation).

Note that bash doesn't have programmed completion itself, but there's a separate bash-completion project which you might be using where completion of .java files for the java command was added in May 2024. That completer is very rudimentary compared to zsh's.

• menteith: Many thanks for this. Could you have a look at my updated question?