[Java] Add killActor API in Java (#6728)

* Add killActor API in Java

* fix javadoc

* update test case

* Address comments

java/runtime/src/main/java/org/ray/runtime/RayDevRuntime.java

@@ -2,6 +2,7 @@ package org.ray.runtime;
 
 import java.util.concurrent.atomic.AtomicInteger;
 
+import org.ray.api.RayActor;
 import org.ray.api.id.JobId;
 import org.ray.api.id.UniqueId;
 import org.ray.runtime.config.RayConfig;
@@ -47,6 +48,11 @@ public class RayDevRuntime extends AbstractRayRuntime {
     LOGGER.error("Not implemented under SINGLE_PROCESS mode.");
   }
 
+  @Override
+  public void killActor(RayActor<?> actor) {
+    throw new UnsupportedOperationException();
+  }
+
   @Override
   public Object getAsyncContext() {
     return null;

java/runtime/src/main/java/org/ray/runtime/RayMultiWorkerNativeRuntime.java

@@ -140,6 +140,11 @@ public class RayMultiWorkerNativeRuntime implements RayRuntime {
     getCurrentRuntime().setResource(resourceName, capacity, nodeId);
   }
 
+  @Override
+  public void killActor(RayActor<?> actor) {
+    getCurrentRuntime().killActor(actor);
+  }
+
   @Override
   public RayObject call(RayFunc func, Object[] args, CallOptions options) {
     return getCurrentRuntime().call(func, args, options);

java/runtime/src/main/java/org/ray/runtime/RayNativeRuntime.java

@@ -6,8 +6,10 @@ import java.io.IOException;
 import java.util.HashMap;
 import java.util.Map;
 import org.apache.commons.io.FileUtils;
+import org.ray.api.RayActor;
 import org.ray.api.id.JobId;
 import org.ray.api.id.UniqueId;
+import org.ray.runtime.actor.NativeRayActor;
 import org.ray.runtime.config.RayConfig;
 import org.ray.runtime.context.NativeWorkerContext;
 import org.ray.runtime.functionmanager.FunctionManager;
@@ -127,6 +129,14 @@ public final class RayNativeRuntime extends AbstractRayRuntime {
     nativeSetResource(nativeCoreWorkerPointer, resourceName, capacity, nodeId.getBytes());
   }
 
+  @Override
+  public void killActor(RayActor<?> actor) {
+    if (!((NativeRayActor) actor).isDirectCallActor()) {
+      throw new UnsupportedOperationException("Only direct call actors can be killed.");
+    }
+    nativeKillActor(nativeCoreWorkerPointer, actor.getId().getBytes());
+  }
+
   @Override
   public Object getAsyncContext() {
     return null;
@@ -184,4 +194,6 @@ public final class RayNativeRuntime extends AbstractRayRuntime {
 
   private static native void nativeSetResource(long conn, String resourceName, double capacity,
       byte[] nodeId);
+
+  private static native void nativeKillActor(long nativeCoreWorkerPointer, byte[] actorId);
 }