Latest updates for jruby.sh

* Check for Java required Java version using .java-version file.
* Interpret "1.8" version as "8".
* Handle missing release file by assuming Java 8.
* Handle missing .java-version file by assuming Java 8 minimum.

Author: headius

exe/jruby.sh

@@ -505,7 +505,21 @@ fi
 
 # ----- Detect Java version and determine available features ------------------
 # shellcheck source=/dev/null
-java_version=$(. "$JAVA_HOME/release" && echo "${JAVA_VERSION-}")
+if [ -f "$JAVA_HOME/release" ]; then
+    java_version=$(. "$JAVA_HOME/release" && echo "${JAVA_VERSION-}")
+    if echo "${java_version}" | grep -q "1.8.\\.*"; then
+        java_version=8
+    fi
+else
+    java_version=8
+fi
+# shellcheck source=/dev/null
+if [ -f "$JRUBY_HOME/bin/.java-version" ]; then
+    minimum_java_version=$(. "$JRUBY_HOME/bin/.java-version" && echo "${JRUBY_MINIMUM_JAVA_VERSION-}")
+else
+    # Only 9.4.12.0 and earlier will have shipped without a .java-version file, so fall back on minimum of 8
+    minimum_java_version=8
+fi
 add_log "Detected Java version: $java_version"
 
 # Split version out for integer comparisons
@@ -522,6 +536,14 @@ readonly java_has_appcds
 # Default to using AppCDS if available
 use_jsa_file="$java_has_appcds"
 
+# Present a useful error if running a Java version lower than bin/.java-version
+if [ "$java_major" -lt "$minimum_java_version" ]; then
+    echo "This version of JRuby requires Java ${minimum_java_version}+."
+    echo "Make sure JAVA_HOME points at JDK ${minimum_java_version} or higher"
+    echo "Current JAVA_HOME: $JAVA_HOME"
+    exit 1
+fi
+
 # AppCDS autogeneration
 if [ "$java_major" -ge 19 ]; then
     java_has_appcds_autogenerate=true