Java doc: "Starting Ray" page (#10062)

java/api/src/main/java/io/ray/api/Ray.java

@@ -37,7 +37,7 @@ public final class Ray extends RayCall {
    *
    * @param factory A factory that produces the runtime instance.
    */
-  public static synchronized void init(RayRuntimeFactory factory) {
+  private static synchronized void init(RayRuntimeFactory factory) {
     if (runtime == null) {
       runtime = factory.createRayRuntime();
       Runtime.getRuntime().addShutdownHook(new Thread(Ray::shutdown));
@@ -54,6 +54,14 @@ public final class Ray extends RayCall {
     }
   }
 
+  /**
+   * Check if {@link #init} has been called yet.
+   * @return True if {@link #init} has already been called and false otherwise.
+   */
+  public static boolean isInitialized() {
+    return runtime != null;
+  }
+
   /**
    * Store an object in the object store.
    *