[Java] Refactor java api (#8858)

java/tutorial/src/main/java/io/ray/exercise/Exercise01.java

@@ -29,8 +29,8 @@ public class Exercise01 implements Serializable {
       // Use `Ray.init` to initialize the Ray runtime.
       Ray.init();
       // Use `Ray.call` to call a remote function.
-      ObjectRef<String> hello = Ray.call(Exercise01::sayHello);
-      ObjectRef<String> world = Ray.call(Exercise01::sayWorld);
+      ObjectRef<String> hello = Ray.task(Exercise01::sayHello).remote();
+      ObjectRef<String> world = Ray.task(Exercise01::sayWorld).remote();
       System.out.println("First remote call result:" + hello.get());
       System.out.println("Second remote call result:" + world.get());
     } catch (Throwable t) {

java/tutorial/src/main/java/io/ray/exercise/Exercise02.java

@@ -28,10 +28,10 @@ public class Exercise02 {
   }
 
   public static String sayHelloWorld() {
-    ObjectRef<String> hello = Ray.call(Exercise02::sayHello);
-    ObjectRef<String> world = Ray.call(Exercise02::sayWorld);
+    ObjectRef<String> hello = Ray.task(Exercise02::sayHello).remote();
+    ObjectRef<String> world = Ray.task(Exercise02::sayWorld).remote();
     // Pass unfinished results as the parameters to another remote function.
-    return Ray.call(Exercise02::merge, hello, world).get();
+    return Ray.task(Exercise02::merge, hello, world).remote().get();
   }
 
   public static void main(String[] args) throws Exception {

java/tutorial/src/main/java/io/ray/exercise/Exercise03.java

@@ -14,7 +14,7 @@ public class Exercise03 {
   public static String sayHelloWithWorld() {
     String ret = "hello";
     System.out.println(ret);
-    ObjectRef<String> world = Ray.call(Exercise03::sayWorld);
+    ObjectRef<String> world = Ray.task(Exercise03::sayWorld).remote();
     return ret + "," + world.get();
   }
 
@@ -30,7 +30,7 @@ public class Exercise03 {
   public static void main(String[] args) throws Exception {
     try {
       Ray.init();
-      String helloWithWorld = Ray.call(Exercise03::sayHelloWithWorld).get();
+      String helloWithWorld = Ray.task(Exercise03::sayHelloWithWorld).remote().get();
       System.out.println(helloWithWorld);
     } catch (Throwable t) {
       t.printStackTrace();

java/tutorial/src/main/java/io/ray/exercise/Exercise04.java

@@ -39,9 +39,9 @@ public class Exercise04 {
     try {
       Ray.init();
       List<ObjectRef<String>> waitList = ImmutableList.of(
-          Ray.call(Exercise04::f1),
-          Ray.call(Exercise04::f2),
-          Ray.call(Exercise04::f3)
+          Ray.task(Exercise04::f1).remote(),
+          Ray.task(Exercise04::f2).remote(),
+          Ray.task(Exercise04::f3).remote()
       );
       // Ray.wait will block until specified number of results are ready
       // or specified timeout have passed.

java/tutorial/src/main/java/io/ray/exercise/Exercise05.java

@@ -13,11 +13,11 @@ public class Exercise05 {
     try {
       Ray.init();
       // `Ray.createActor` creates an actor instance.
-      ActorHandle<Adder> adder = Ray.createActor(Adder::new, 0);
-      // Use `Ray.call(actor, parameters)` to call an actor method.
-      ObjectRef<Integer> result1 = adder.call(Adder::add, 1);
+      ActorHandle<Adder> adder = Ray.actor(Adder::new, 0).remote();
+      // Use `Ray.task(actor, parameters).remote()` to call an actor method.
+      ObjectRef<Integer> result1 = adder.task(Adder::add, 1).remote();
       System.out.println(result1.get());
-      ObjectRef<Integer> result2 = adder.call(Adder::add, 10);
+      ObjectRef<Integer> result2 = adder.task(Adder::add, 10).remote();
       System.out.println(result2.get());
     } catch (Throwable t) {
       t.printStackTrace();