Autocompletion in Java Source Files with zsh
In this article, we will explore how to enable autocompletion for Java source files using the zsh shell. Java is a popular programming language, and providing autocompletion features can dramatically improve the developer experience while working in the terminal.
What is zsh?
The Z shell (zsh) is a Unix shell that can be used as an interactive login shell and as a scripting language interpreter. zsh is an extended shell with many improvements over traditional shells like bash, including a powerful autocompletion system.
Java Source File Autocompletion
To enable autocompletion for Java source files (.java), you need to add a custom completion
function to your zsh configuration file (usually ~/.zshrc). To get started, create a new file
called _java in the ${fpath[1]} directory, which is typically
/usr/share/zsh/site-functions/.
# Create the _java file in the site-functions directory
$ echo "<function>" >> \
/usr/share/zsh/site-functions/_java
$ echo "_java() {" >> \
/usr/share/zsh/site-functions/_java
Parsing Java Source Files
To parse Java source files for autocompletion, you can use the ctags tool.
ctags generates a tags file that contains information about the structure of the code,
including class and method definitions. First, make sure you have exuberant-ctags installed
on your system:
# Install exuberant-ctags (Ubuntu/Debian)
$ sudo apt-get install exuberant-ctags
Next, create a function in the _java file to parse a Java source file and
generate a tags file:
# Function to parse a Java source file and generate a tags file
parse_java_file() {
local file=$1
if [[ -f $file ]]; then
ctags -R -f /tmp/java_tags --langmap=java:.java --fields=+l --extra=+q $file
fi
}Autocompletion Function
Now, create the main autocompletion function that will use the tags file to provide autocompletion suggestions:
# Autocompletion function using the tags file
_java_classes() {
local tags_file=/tmp/java_tags
if [[ -f $tags_file ]]; then
local words=(${=words[@]})
local word=${words[-1]}
local line lines
if [[ $word == \<*\> ]]; then
word=${word#\<}
word=${word%\>}
fi
lines=(${(f)"$(grep -w $word $tags_file | cut -f2 -d:)"})
reply=( ${(k)lines} )
fi
}
Update your zsh configuration file (~/.zshrc) to load the new _java
file and set up the autocompletion function for Java source files:
# Load the _java file and set up the autocompletion function
source /usr/share/zsh/site-functions/\_java
zstyle ':completion:*:java:*' tag-order \
classes methods
zstyle ':completion:*:java:*' completions \
/usr/share/zsh/site-functions/\_java
compdef _java java
Using Java Autocompletion
After reloading your zsh configuration (source ~/.zshrc), you can now use
autocompletion for Java source files. Start typing the name of a Java class or method, and
press the TAB key to see the available suggestions:
MyClass MyOtherClass
```