fix checkstyle

Author: yanmin

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/service/launcher/IrqHandler.java

@@ -47,18 +47,18 @@ public final class IrqHandler implements SignalHandler {
   /**
    * Definition of the Control-C handler name: {@value}.
    */
-  public static final Signal CONTROL_C = Signal.SIGINT;
+  public static final String CONTROL_C = "SIGINT";
 
   /**
    * Definition of default <code>kill</code> signal: {@value}.
    */
-  public static final Signal SIGTERM = Signal.SIGTERM;
+  public static final String SIGTERM = "SIGTERM";
 
   /**
    * Handler to relay to.
    */
   private final Interrupted handler;
-  private static final POSIX posix = POSIXFactory.getNativePOSIX();
+  private static final POSIX POSIX_IMPL = POSIXFactory.getNativePOSIX();
 
   /** Count of how many times a signal has been raised. */
   private final AtomicInteger signalCount = new AtomicInteger(0);
@@ -86,7 +86,7 @@ public IrqHandler(Signal signal, Interrupted handler) {
    */
   public void bind() {
     try {
-      posix.signal(signal, this);
+      POSIX_IMPL.signal(signal, this);
     } catch (IllegalArgumentException e) {
       throw new IllegalArgumentException(
           "Could not set handler for signal \"" + signal + "\"."
@@ -106,7 +106,7 @@ public String getName() {
    * Raise the signal.
    */
   public void raise() {
-    posix.kill(posix.getpid(), signal.intValue());
+    POSIX_IMPL.kill(POSIX_IMPL.getpid(), signal.intValue());
   }
 
   @Override

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/service/launcher/ServiceLauncher.java

@@ -761,8 +761,8 @@ protected void registerFailureHandling() {
     try {
       interruptEscalator = new InterruptEscalator(this,
           SHUTDOWN_TIME_ON_INTERRUPT);
-      interruptEscalator.register(IrqHandler.CONTROL_C.name());
-      interruptEscalator.register(IrqHandler.SIGTERM.name());
+      interruptEscalator.register(IrqHandler.CONTROL_C);
+      interruptEscalator.register(IrqHandler.SIGTERM);
     } catch (IllegalArgumentException e) {
       // downgrade interrupt registration to warnings
       LOG.warn("{}", e, e);

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/SignalLogger.java

@@ -39,7 +39,8 @@
 @InterfaceStability.Unstable
 public enum SignalLogger {
   INSTANCE;
-  private static final Set<Signal> SIGNALS = EnumSet.of(Signal.SIGHUP, Signal.SIGINT, Signal.SIGTERM);
+  private static final Set<Signal> SIGNALS =
+          EnumSet.of(Signal.SIGHUP, Signal.SIGINT, Signal.SIGTERM);
   private static final POSIX POSIX_IMPL = POSIXFactory.getJavaPOSIX();
   private static final SignalHandler DEFAULT_HANDLER = System::exit;