Get latest java home version for stable image

Author: sarahchen6

gradle/java_no_deps.gradle

@@ -151,7 +151,15 @@ project.afterEvaluate {
   def testJvm = gradle.startParameter.projectProperties["testJvm"]
   def javaTestLauncher = null as Provider<JavaLauncher>
   if (testJvm == "stable") {
-    testJvm = "24"
+    def javaHomeVersions = System.getenv().findAll { it.key =~ /^JAVA_[0-9]+_HOME$/ }
+    if (javaHomeVersions.isEmpty()) {
+      throw new GradleException("No JAVA_X_HOME environment variables found.")
+    }
+    def latestVersion = javaHomeVersions.keySet().collect { key ->
+      def matcher = key =~ /JAVA_([0-9]+)_HOME/
+      matcher.group(1) as Integer
+    }.max()
+    testJvm = latestVersion.toString()
   }
   if (testJvm) {
     def matcher = testJvm =~ /([a-zA-Z]*)([0-9]+)/