[SPARK-14011][CORE][SQL] Enable `LineLength` Java checkstyle rule

## What changes were proposed in this pull request?

[Spark Coding Style Guide](https://cwiki.apache.org/confluence/display/SPARK/Spark+Code+Style+Guide) has 100-character limit on lines, but it's disabled for Java since 11/09/15. This PR enables **LineLength** checkstyle again. To help that, this also introduces **RedundantImport** and **RedundantModifier**, too. The following is the diff on `checkstyle.xml`.

```xml
-        <!-- TODO: 11/09/15 disabled - the lengths are currently > 100 in many places -->
-        <!--
         <module name="LineLength">
             <property name="max" value="100"/>
             <property name="ignorePattern" value="^package.*|^import.*|a href|href|http://|https://|ftp://"/>
         </module>
-        -->
         <module name="NoLineWrap"/>
         <module name="EmptyBlock">
             <property name="option" value="TEXT"/>
 -167,5 +164,7
         </module>
         <module name="CommentsIndentation"/>
         <module name="UnusedImports"/>
+        <module name="RedundantImport"/>
+        <module name="RedundantModifier"/>
```

## How was this patch tested?

Currently, `lint-java` is disabled in Jenkins. It needs a manual test.
After passing the Jenkins tests, `dev/lint-java` should passes locally.

Author: Dongjoon Hyun <dongjoon@apache.org>

Closes #11831 from dongjoon-hyun/SPARK-14011.

3 files changed, 3 insertions, 3 deletions

diff --git a/launcher/src/main/java/org/apache/spark/launcher/AbstractCommandBuilder.java b/launcher/src/main/java/org/apache/spark/launcher/AbstractCommandBuilder.java
index f6c7e07654..587fda7a3c 100644
--- a/launcher/src/main/java/org/apache/spark/launcher/AbstractCommandBuilder.java
+++ b/launcher/src/main/java/org/apache/spark/launcher/AbstractCommandBuilder.java
@@ -57,7 +57,7 @@ abstract class AbstractCommandBuilder {
   // properties files multiple times.
   private Map<String, String> effectiveConfig;
 
-  public AbstractCommandBuilder() {
+  AbstractCommandBuilder() {
     this.appArgs = new ArrayList<>();
     this.childEnv = new HashMap<>();
     this.conf = new HashMap<>();
diff --git a/launcher/src/main/java/org/apache/spark/launcher/CommandBuilderUtils.java b/launcher/src/main/java/org/apache/spark/launcher/CommandBuilderUtils.java
index 37afafea28..39fdf300e2 100644
--- a/launcher/src/main/java/org/apache/spark/launcher/CommandBuilderUtils.java
+++ b/launcher/src/main/java/org/apache/spark/launcher/CommandBuilderUtils.java
@@ -32,7 +32,7 @@ class CommandBuilderUtils {
   static final String ENV_SPARK_HOME = "SPARK_HOME";
 
   /** The set of known JVM vendors. */
-  static enum JavaVendor {
+  enum JavaVendor {
     Oracle, IBM, OpenJDK, Unknown
   };
 
diff --git a/launcher/src/main/java/org/apache/spark/launcher/SparkAppHandle.java b/launcher/src/main/java/org/apache/spark/launcher/SparkAppHandle.java
index e9caf0b3cb..625d026321 100644
--- a/launcher/src/main/java/org/apache/spark/launcher/SparkAppHandle.java
+++ b/launcher/src/main/java/org/apache/spark/launcher/SparkAppHandle.java
@@ -32,7 +32,7 @@ public interface SparkAppHandle {
    *
    * @since 1.6.0
    */
-  public enum State {
+  enum State {
     /** The application has not reported back yet. */
     UNKNOWN(false),
     /** The application has connected to the handle. */