[Java] Refine tests and fix single-process mode (#4265)

python/ray/services.py

@@ -1242,7 +1242,7 @@ def build_java_worker_command(
     """
     assert java_worker_options is not None
 
-    command = "java {} ".format(java_worker_options)
+    command = "java ".format(java_worker_options)
     if redis_address is not None:
         command += "-Dray.redis.address={} ".format(redis_address)
 
@@ -1259,6 +1259,11 @@ def build_java_worker_command(
     command += "-Dray.home={} ".format(RAY_HOME)
     # TODO(suquark): We should use temp_dir as the input of a java worker.
     command += "-Dray.log-dir={} ".format(os.path.join(temp_dir, "sockets"))
+
+    if java_worker_options:
+        # Put `java_worker_options` in the last, so it can overwrite the
+        # above options.
+        command += java_worker_options + " "
     command += "org.ray.runtime.runner.worker.DefaultWorker"
 
     return command

python/setup.py

@@ -80,7 +80,11 @@ class build_ext(_build_ext.build_ext):
         # version of Python to build pyarrow inside the build.sh script. Note
         # that certain flags will not be passed along such as --user or sudo.
         # TODO(rkn): Fix this.
-        subprocess.check_call(["../build.sh", "-p", sys.executable])
+        command = ["../build.sh", "-p", sys.executable]
+        if os.getenv("RAY_INSTALL_JAVA") == "1":
+            # Also build binaries for Java if the above env variable exists.
+            command += ["-l", "python,java"]
+        subprocess.check_call(command)
 
         # We also need to install pyarrow along with Ray, so make sure that the
         # relevant non-Python pyarrow files get copied.