Apply pmd plugin and fix/ignore broken styles

This commit applies [p3c-pmd](https://github.com/alibaba/p3c) plugin/rules, and fixes/ignores all violations of piority 1 (mandatory).

core/src/main/java/com/taobao/arthas/core/command/monitor200/DashboardCommand.java

@@ -47,6 +47,7 @@ import java.util.TimerTask;
         "  dashboard -n 10\n" +
         "  dashboard -i 2000\n" +
         Constants.WIKI + Constants.WIKI_HOME + "dashboard")
+@SuppressWarnings("PMD.AvoidUseTimerRule")
 public class DashboardCommand extends AnnotatedCommand {
 
     private static final Logger logger = LogUtil.getArthasLogger();

core/src/main/java/com/taobao/arthas/core/command/monitor200/DashboardInterruptHandler.java

@@ -8,6 +8,7 @@ import java.util.Timer;
 /**
  * @author ralf0131 2017-01-09 13:37.
  */
+@SuppressWarnings("PMD.AvoidUseTimerRule")
 public class DashboardInterruptHandler extends CommandInterruptHandler {
 
     private volatile Timer timer;

core/src/main/java/com/taobao/arthas/core/command/monitor200/MonitorAdviceListener.java

@@ -66,6 +66,7 @@ import static com.taobao.text.ui.Element.label;
  *
  * @author beiwei30 on 28/11/2016.
  */
+@SuppressWarnings("PMD.AvoidUseTimerRule")
 class MonitorAdviceListener extends ReflectAdviceListenerAdapter {
     // 输出定时任务
     private Timer timer;

core/src/main/java/com/taobao/arthas/core/server/ArthasBootstrap.java

@@ -40,6 +40,7 @@ public class ArthasBootstrap {
     private ShellServer shellServer;
     private ExecutorService executorService;
 
+    @SuppressWarnings("PMD.ThreadPoolCreationRule")
     private ArthasBootstrap(int pid, Instrumentation instrumentation) {
         this.pid = pid;
         this.instrumentation = instrumentation;

core/src/main/java/com/taobao/arthas/core/shell/impl/ShellServerImpl.java

@@ -146,6 +146,7 @@ public class ShellServerImpl extends ShellServer {
         }
     }
 
+    @SuppressWarnings("PMD.ThreadPoolCreationRule")
     public synchronized void setTimer() {
         if (!closed && reaperInterval > 0) {
             scheduledExecutorService = Executors.newSingleThreadScheduledExecutor();

core/src/main/java/com/taobao/arthas/core/shell/system/impl/GlobalJobControllerImpl.java

@@ -22,7 +22,7 @@ import com.taobao.middleware.logger.Logger;
  * @author gehui 2017年7月31日 上午11:55:41
  */
 public class GlobalJobControllerImpl extends JobControllerImpl {
-
+    @SuppressWarnings("PMD.AvoidUseTimerRule")
     private Timer timer = new Timer("job-timeout", true);
     private Map<Integer, TimerTask> jobTimeoutTaskMap = new HashMap<Integer, TimerTask>();
     private static final Logger logger = LogUtil.getArthasLogger();

core/src/main/java/com/taobao/arthas/core/util/Decompiler.java

@@ -85,14 +85,16 @@ public class Decompiler {
             path = classFileSource.adjustInputPath(path);
 
             AnalysisType type = (AnalysisType) options.getOption(OptionsImpl.ANALYSE_AS);
-            if (type == null)
+            if (type == null) {
                 type = dcCommonState.detectClsJar(path);
+            }
 
             if (type == AnalysisType.JAR) {
                 // doJar(dcCommonState, path, dumperFactory);
             }
-            if (type == AnalysisType.CLASS)
+            if (type == AnalysisType.CLASS) {
                 result.append(doClass(dcCommonState, path, skipInnerClass, dumperFactory));
+            }
         }
         return result.toString();
     }
@@ -105,8 +107,9 @@ public class Decompiler {
         Dumper d = new ToStringDumper();
         try {
             ClassFile c = dcCommonState.getClassFileMaybePath(path);
-            if ((skipInnerClass) && (c.isInnerClass()))
+            if ((skipInnerClass) && (c.isInnerClass())) {
                 return "";
+            }
             dcCommonState.configureWith(c);
             dumperFactory.getProgressDumper().analysingType(c.getClassType());
             try {
@@ -132,12 +135,14 @@ public class Decompiler {
             // collectingDumper.getTypeUsageInformation(), illegalIdentifierDump);
 
             String methname = (String) options.getOption(OptionsImpl.METHODNAME);
-            if (methname == null)
+            if (methname == null) {
                 c.dump(d);
+            }
             else {
                 try {
-                    for (Method method : c.getMethodByName(methname))
+                    for (Method method : c.getMethodByName(methname)) {
                         method.dump(d, true);
+                    }
                 } catch (NoSuchMethodException e) {
                     throw new IllegalArgumentException("No such method '" + methname + "'.");
                 }
@@ -146,18 +151,21 @@ public class Decompiler {
             result.append(d.toString());
         } catch (ConfusedCFRException e) {
             result.append(e.toString()).append("\n");
-            for (Object x : e.getStackTrace())
+            for (Object x : e.getStackTrace()) {
                 result.append(x).append("\n");
+            }
         } catch (CannotLoadClassException e) {
             result.append("Can't load the class specified:").append("\n");
             result.append(e.toString()).append("\n");
         } catch (RuntimeException e) {
             result.append(e.toString()).append("\n");
-            for (Object x : e.getStackTrace())
+            for (Object x : e.getStackTrace()) {
                 result.append(x).append("\n");
+            }
         } finally {
-            if (d != null)
+            if (d != null) {
                 d.close();
+            }
         }
         return result.toString();
     }

core/src/main/java/com/taobao/arthas/core/util/NetUtils.java

@@ -191,12 +191,13 @@ public class NetUtils {
         } catch (Exception e) {
             return false;
         } finally {
-            if (s != null)
+            if (s != null) {
                 try {
                     s.close();
                 } catch (Exception e) {
                     // ignore
                 }
+            }
         }
     }
 

core/src/main/java/com/taobao/arthas/core/util/StringUtils.java

@@ -871,7 +871,9 @@ public abstract class StringUtils {
     }
 
     public static String classLoaderHash(Class<?> clazz) {
-        if (clazz == null || clazz.getClassLoader() == null) return "null";
+        if (clazz == null || clazz.getClassLoader() == null) {
+            return "null";
+        }
         return Integer.toHexString(clazz.getClassLoader().hashCode());
     }
 
@@ -881,7 +883,9 @@ public abstract class StringUtils {
      * @return  human readable format
      */
     public static String humanReadableByteCount(long bytes) {
-        if (bytes < UNIT) return bytes + " B";
+        if (bytes < UNIT) {
+            return bytes + " B";
+        }
         int exp = (int) (Math.log(bytes) / Math.log(UNIT));
         String pre =  STRING_UNITS.charAt(exp-1) +  "i";
         return String.format("%.2f %sB", bytes / Math.pow(UNIT, exp), pre);

core/src/main/java/com/taobao/arthas/core/util/UserStatUtil.java

@@ -15,6 +15,7 @@ import java.util.concurrent.Executors;
  * Created by zhuyong on 15/11/12.
  */
 public class UserStatUtil {
+    @SuppressWarnings("PMD.ThreadPoolCreationRule")
     private static final ExecutorService executorService = Executors.newSingleThreadExecutor();
     private static final String ip = IPUtils.getLocalIP();
 

core/src/main/java/com/taobao/arthas/core/view/Ansi.java

@@ -136,7 +136,9 @@ public class Ansi {
     };
 
     public static void setDetector(final Callable<Boolean> detector) {
-        if (detector == null) throw new IllegalArgumentException();
+        if (detector == null) {
+            throw new IllegalArgumentException();
+        }
         Ansi.detector = detector;
     }
 
@@ -698,8 +700,9 @@ public class Ansi {
     }
 
     private void flushAttributes() {
-        if (attributeOptions.isEmpty())
+        if (attributeOptions.isEmpty()) {
             return;
+        }
         if (attributeOptions.size() == 1 && attributeOptions.get(0) == 0) {
             builder.append(FIRST_ESC_CHAR);
             builder.append(SECOND_ESC_CHAR);