[SPARK-12489][CORE][SQL][MLIB] Fix minor issues found by FindBugs

Include the following changes:

1. Close `java.sql.Statement`
2. Fix incorrect `asInstanceOf`.
3. Remove unnecessary `synchronized` and `ReentrantLock`.

Author: Shixiong Zhu <shixiong@databricks.com>

Closes #10440 from zsxwing/findbugs.

2 files changed, 2 insertions, 4 deletions

diff --git a/launcher/src/main/java/org/apache/spark/launcher/LauncherServer.java b/launcher/src/main/java/org/apache/spark/launcher/LauncherServer.java
index d099ee9aa9..414ffc2c84 100644
--- a/launcher/src/main/java/org/apache/spark/launcher/LauncherServer.java
+++ b/launcher/src/main/java/org/apache/spark/launcher/LauncherServer.java
@@ -293,9 +293,7 @@ class LauncherServer implements Closeable {
     protected void handle(Message msg) throws IOException {
       try {
         if (msg instanceof Hello) {
-          synchronized (timeout) {
-            timeout.cancel();
-          }
+          timeout.cancel();
           timeout = null;
           Hello hello = (Hello) msg;
           ChildProcAppHandle handle = pending.remove(hello.secret);
diff --git a/launcher/src/main/java/org/apache/spark/launcher/Main.java b/launcher/src/main/java/org/apache/spark/launcher/Main.java
index a4e3acc674..e751e948e3 100644
--- a/launcher/src/main/java/org/apache/spark/launcher/Main.java
+++ b/launcher/src/main/java/org/apache/spark/launcher/Main.java
@@ -151,7 +151,7 @@ class Main {
 
     @Override
     protected boolean handle(String opt, String value) {
-      if (opt == CLASS) {
+      if (CLASS.equals(opt)) {
         className = value;
       }
       return false;