[FLINK-23909][connector-jdbc][scala-shell][yarn] Remove redundant variables and improve some style format in coding.

This closes apache#16931.

Author: RocMarshal

flink-connectors/flink-connector-jdbc/src/test/java/org/apache/flink/connector/jdbc/JdbcDataTypeTest.java

@@ -149,7 +149,7 @@ public static List<TestItem> testData() {
 
     private static TestItem createTestItem(Object... args) {
         assert args.length >= 2;
-        TestItem item = TestItem.fromDialetAndType((String) args[0], (String) args[1]);
+        TestItem item = TestItem.fromDialectAndType((String) args[0], (String) args[1]);
         if (args.length == 3) {
             item.withExpectError((String) args[2]);
         }
@@ -193,7 +193,7 @@ private TestItem(String dialect, String dataTypeExpr) {
             this.dataTypeExpr = dataTypeExpr;
         }
 
-        static TestItem fromDialetAndType(String dialect, String dataTypeExpr) {
+        static TestItem fromDialectAndType(String dialect, String dataTypeExpr) {
             return new TestItem(dialect, dataTypeExpr);
         }
 

flink-connectors/flink-connector-jdbc/src/test/java/org/apache/flink/connector/jdbc/catalog/PostgresCatalogTestBase.java

@@ -189,7 +189,7 @@ public static TestTable getPrimitiveTable() {
     }
 
     // TODO: add back timestamptz and time types.
-    //  Flink currently doens't support converting time's precision, with the following error
+    //  Flink currently doesn't support converting time's precision, with the following error
     //  TableException: Unsupported conversion from data type 'TIME(6)' (conversion class:
     // java.sql.Time)
     //  to type information. Only data types that originated from type information fully support a

flink-connectors/flink-connector-jdbc/src/test/java/org/apache/flink/connector/jdbc/xa/JdbcExactlyOnceSinkE2eTest.java

@@ -234,7 +234,9 @@ public void testInsert() throws Exception {
                 insertedIds.toString(),
                 insertedIds.size() == expectedIds.size() && expectedIds.containsAll(insertedIds));
         LOG.info(
-                "Test insert for {} finished in {}ms", dbEnv, System.currentTimeMillis() - started);
+                "Test insert for {} finished in {} ms.",
+                dbEnv,
+                System.currentTimeMillis() - started);
     }
 
     @Override

flink-scala-shell/src/main/java/org/apache/flink/api/java/JarHelper.java

@@ -86,14 +86,12 @@ public void jarDir(File dirOrFile2Jar, File destJar) throws IOException {
 
     /** Unjars a given jar file into a given directory. */
     public void unjarDir(File jarFile, File destDir) throws IOException {
-        BufferedOutputStream dest = null;
         FileInputStream fis = new FileInputStream(jarFile);
         unjar(fis, destDir);
     }
 
     /** Given an InputStream on a jar file, unjars the contents into the given directory. */
     public void unjar(InputStream in, File destDir) throws IOException {
-        BufferedOutputStream dest = null;
         JarInputStream jis = new JarInputStream(in);
         JarEntry entry;
         while ((entry = jis.getNextJarEntry()) != null) {
@@ -112,7 +110,7 @@ public void unjar(InputStream in, File destDir) throws IOException {
                 System.out.println("unjarring " + destFile + " from " + entry.getName());
             }
             FileOutputStream fos = new FileOutputStream(destFile);
-            dest = new BufferedOutputStream(fos, BUFFER_SIZE);
+            BufferedOutputStream dest = new BufferedOutputStream(fos, BUFFER_SIZE);
             try {
                 while ((count = jis.read(data, 0, BUFFER_SIZE)) != -1) {
                     dest.write(data, 0, count);

flink-yarn/src/main/java/org/apache/flink/yarn/cli/FlinkYarnSessionCli.java

@@ -685,7 +685,7 @@ public int run(String[] args) throws CliArgsException, FlinkException {
     }
 
     private void shutdownCluster(
-            ClusterClient clusterClient,
+            ClusterClient<ApplicationId> clusterClient,
             ScheduledExecutorService scheduledExecutorService,
             YarnApplicationStatusMonitor yarnApplicationStatusMonitor) {
         try {
@@ -827,7 +827,7 @@ public static Map<String, String> getDynamicProperties(String dynamicPropertiesE
 
                 if (firstEquals >= 0) {
                     String key = propLine.substring(0, firstEquals).trim();
-                    String value = propLine.substring(firstEquals + 1, propLine.length()).trim();
+                    String value = propLine.substring(firstEquals + 1).trim();
 
                     if (!key.isEmpty()) {
                         properties.put(key, value);