[MINOR][BUILD] Fix about 15 misc build warnings

### What changes were proposed in this pull request?

This addresses about 15 miscellaneous warnings that appear in the current build.

### Why are the changes needed?

No functional changes, it just slightly reduces the amount of extra warning output.

### Does this PR introduce any user-facing change?

No.

### How was this patch tested?

Existing tests, run manually.

Closes #25852 from srowen/BuildWarnings.

Authored-by: Sean Owen <sean.owen@databricks.com>
Signed-off-by: Dongjoon Hyun <dhyun@apple.com>

common/kvstore/src/main/java/org/apache/spark/util/kvstore/InMemoryStore.java

@@ -252,7 +252,7 @@ public class InMemoryStore implements KVStore {
 
         return (value) -> set.contains(indexValueForEntity(getter, value));
       } else {
-        HashSet<Comparable> set = new HashSet<>(values.size());
+        HashSet<Comparable<?>> set = new HashSet<>(values.size());
         for (Object key : values) {
           set.add(asKey(key));
         }

common/kvstore/src/main/java/org/apache/spark/util/kvstore/KVTypeInfo.java

@@ -124,7 +124,7 @@ public class KVTypeInfo {
 
     Object get(Object instance) throws ReflectiveOperationException;
 
-    Class getType();
+    Class<?> getType();
   }
 
   private class FieldAccessor implements Accessor {
@@ -141,7 +141,7 @@ public class KVTypeInfo {
     }
 
     @Override
-    public Class getType() {
+    public Class<?> getType() {
       return field.getType();
     }
   }
@@ -160,7 +160,7 @@ public class KVTypeInfo {
     }
 
     @Override
-    public Class getType() {
+    public Class<?> getType() {
       return method.getReturnType();
     }
   }

core/src/test/java/org/apache/spark/shuffle/sort/UnsafeShuffleWriterSuite.java

@@ -172,9 +172,9 @@ public class UnsafeShuffleWriterSuite {
     when(taskContext.taskMemoryManager()).thenReturn(taskMemoryManager);
   }
 
-  private UnsafeShuffleWriter createWriter(boolean transferToEnabled) {
+  private UnsafeShuffleWriter<Object, Object> createWriter(boolean transferToEnabled) {
     conf.set("spark.file.transferTo", String.valueOf(transferToEnabled));
-    return new UnsafeShuffleWriter(
+    return new UnsafeShuffleWriter<>(
       blockManager,
         taskMemoryManager,
       new SerializedShuffleHandle<>(0, 1, shuffleDep),
@@ -533,7 +533,7 @@ public class UnsafeShuffleWriterSuite {
     final long numRecordsPerPage = pageSizeBytes / recordLengthBytes;
     taskMemoryManager = spy(taskMemoryManager);
     when(taskMemoryManager.pageSizeBytes()).thenReturn(pageSizeBytes);
-    final UnsafeShuffleWriter writer = new UnsafeShuffleWriter(
+    final UnsafeShuffleWriter<Object, Object> writer = new UnsafeShuffleWriter<>(
         blockManager,
         taskMemoryManager,
         new SerializedShuffleHandle<>(0, 1, shuffleDep),

core/src/test/scala/org/apache/spark/deploy/history/HistoryServerSuite.scala

@@ -26,7 +26,6 @@ import javax.servlet.http.{HttpServletRequest, HttpServletRequestWrapper, HttpSe
 import scala.collection.JavaConverters._
 import scala.concurrent.duration._
 
-import com.gargoylesoftware.htmlunit.BrowserVersion
 import com.google.common.io.{ByteStreams, Files}
 import org.apache.commons.io.{FileUtils, IOUtils}
 import org.apache.hadoop.fs.{FileStatus, FileSystem, Path}
@@ -365,8 +364,7 @@ class HistoryServerSuite extends SparkFunSuite with BeforeAndAfter with Matchers
     contextHandler.addServlet(holder, "/")
     server.attachHandler(contextHandler)
 
-    implicit val webDriver: WebDriver =
-      new HtmlUnitDriver(BrowserVersion.INTERNET_EXPLORER_11, true)
+    implicit val webDriver: WebDriver = new HtmlUnitDriver(true)
 
     try {
       val url = s"http://localhost:$port"

core/src/test/scala/org/apache/spark/util/KeyLockSuite.scala

@@ -49,7 +49,7 @@ class KeyLockSuite extends SparkFunSuite with TimeLimits {
     @volatile var e: Throwable = null
     val threads = (0 until numThreads).map { i =>
       new Thread() {
-        override def run(): Unit = try {
+        override def run(): Unit = {
           latch.await(foreverMs, TimeUnit.MILLISECONDS)
           keyLock.withLock(keys(i)) {
             var cur = numThreadsHoldingLock.get()

repl/src/test/scala/org/apache/spark/repl/ExecutorClassLoaderSuite.scala

@@ -272,7 +272,8 @@ class ExecutorClassLoaderSuite
         assert(e.getMessage.contains("ThisIsAClassName"))
         // RemoteClassLoaderError must not be LinkageError nor ClassNotFoundException. Otherwise,
         // JVM will cache it and doesn't retry to load a class.
-        assert(!e.isInstanceOf[LinkageError] && !e.isInstanceOf[ClassNotFoundException])
+        assert(!(classOf[LinkageError].isAssignableFrom(e.getClass)))
+        assert(!(classOf[ClassNotFoundException].isAssignableFrom(e.getClass)))
       } finally {
         rpcEnv.shutdown()
         rpcEnv.awaitTermination()

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/trees/TreeNodeSuite.scala

@@ -680,12 +680,12 @@ class TreeNodeSuite extends SparkFunSuite with SQLHelper {
   }
 
   test("clone") {
-    def assertDifferentInstance(before: AnyRef, after: AnyRef): Unit = {
+    def assertDifferentInstance[T <: TreeNode[T]](before: TreeNode[T], after: TreeNode[T]): Unit = {
       assert(before.ne(after) && before == after)
-      before.asInstanceOf[TreeNode[_]].children.zip(
-          after.asInstanceOf[TreeNode[_]].children).foreach {
-        case (beforeChild: AnyRef, afterChild: AnyRef) =>
-          assertDifferentInstance(beforeChild, afterChild)
+      before.children.zip(after.children).foreach { case (beforeChild, afterChild) =>
+        assertDifferentInstance(
+          beforeChild.asInstanceOf[TreeNode[T]],
+          afterChild.asInstanceOf[TreeNode[T]])
       }
     }