Add a `java_utils.bzl` to `rules_java`

For now, this only exposes a method to tokenize javacopts. This will be useful for both internal and OSS projects once we change the type of `JavaInfo.compilation_info.javac_opts` to a `depset`.

PiperOrigin-RevId: 582301665
Change-Id: I717725ecde348cac73b6ab3050c7712b2261685b

java/BUILD

diff --git a/java/BUILD b/java/BUILD
index a42b374..bf9da91 100644
--- a/java/BUILD
+++ b/java/BUILD
@@ -18,6 +18,12 @@
 )
 
 bzl_library(
+    name = "utils",
+    srcs = ["java_utils.bzl"],
+    visibility = ["//visibility:public"],
+)
+
+bzl_library(
     name = "java_single_jar",
     srcs = ["java_single_jar.bzl"],
     visibility = ["//visibility:public"],

java/java_utils.bzl

diff --git a/java/java_utils.bzl b/java/java_utils.bzl
new file mode 100644
index 0000000..a90a001
--- /dev/null
+++ b/java/java_utils.bzl
@@ -0,0 +1,25 @@
+"""Utility methods for interacting with the java rules"""
+
+def _tokenize_javacopts(ctx, opts):
+    """Tokenizes a list or depset of options to a list.
+
+    Iff opts is a depset, we reverse the flattened list to ensure right-most
+    duplicates are preserved in their correct position.
+
+    Args:
+        ctx: (RuleContext) the rule context
+        opts: (depset[str]|[str]) the javac options to tokenize
+    Returns:
+        [str] list of tokenized options
+    """
+    if hasattr(opts, "to_list"):
+        opts = reversed(opts.to_list())
+    return [
+        token
+        for opt in opts
+        for token in ctx.tokenize(opt)
+    ]
+
+utils = struct(
+    tokenize_javacopts = _tokenize_javacopts,
+)