language/java: document public API

Library/Homebrew/language/java.rb

@@ -28,6 +28,13 @@ def self.find_openjdk_formula(version = nil)
     end
     private_class_method :find_openjdk_formula
 
+    # Returns the directory of the newest matching OpenJDK installation or
+    # `nil` if none is available. When used in a {Formula}, there should be
+    # a dependency and corresponding `version` for reproducible output.
+    #
+    # @api public
+    # @param version OpenJDK version constraint which can be specific
+    #   (e.g. `"21"`) or a lower-bounded range (e.g. `"21+"`)
     sig { params(version: T.nilable(String)).returns(T.nilable(Pathname)) }
     def self.java_home(version = nil)
       find_openjdk_formula(version)&.opt_libexec
@@ -39,11 +46,36 @@ def self.java_home_shell(version = nil)
     end
     private_class_method :java_home_shell
 
+    # Returns a `JAVA_HOME` environment variable to use a specific OpenJDK.
+    # Usually combined with either {Pathname#write_env_script} or
+    # {Pathname#env_script_all_files}.
+    #
+    # ### Example
+    #
+    # Use `openjdk@21` for all commands:
+    #
+    # ```ruby
+    # bin.env_script_all_files libexec/"bin", Language::Java.java_home_env("21")
+    # ```
+    #
+    # @api public
     sig { params(version: T.nilable(String)).returns({ JAVA_HOME: String }) }
     def self.java_home_env(version = nil)
       { JAVA_HOME: java_home_shell(version) }
     end
 
+    # Returns a `JAVA_HOME` environment variable to use a default OpenJDK.
+    # Unlike {.java_home_env} the OpenJDK can be overridden at runtime.
+    #
+    # ### Example
+    #
+    # Use latest `openjdk` as default:
+    #
+    # ```ruby
+    # bin.env_script_all_files libexec/"bin", Language::Java.overridable_java_home_env
+    # ```
+    #
+    # @api public
     sig { params(version: T.nilable(String)).returns({ JAVA_HOME: String }) }
     def self.overridable_java_home_env(version = nil)
       { JAVA_HOME: "${JAVA_HOME:-#{java_home_shell(version)}}" }