string concat in StringBuilder append chain (#1984)

boot/src/main/java/com/taobao/arthas/boot/Bootstrap.java

@@ -694,14 +694,14 @@ public class Bootstrap {
 
         result.append("Local versions:\n");
         for (String version : versionList) {
-            result.append(" " + version).append('\n');
+            result.append(" ").append(version).append('\n');
         }
         result.append("Remote versions:\n");
 
 		List<String> remoteVersions = DownloadUtils.readRemoteVersions();
 		Collections.reverse(remoteVersions);
 		for (String version : remoteVersions) {
-			result.append(" " + version).append('\n');
+			result.append(" ").append(version).append('\n');
 		}
         return result.toString();
     }

core/src/main/java/com/taobao/arthas/core/command/view/TraceView.java

@@ -98,10 +98,10 @@ public class TraceView extends ResultView<TraceModel> {
 
             //trace_id
             if (threadNode.getTraceId() != null) {
-                sb.append(";trace_id="+threadNode.getTraceId());
+                sb.append(";trace_id=").append(threadNode.getTraceId());
             }
             if (threadNode.getRpcId() != null) {
-                sb.append(";rpc_id="+threadNode.getRpcId());
+                sb.append(";rpc_id=").append(threadNode.getRpcId());
             }
         } else if (node instanceof ThrowNode) {
             ThrowNode throwNode = (ThrowNode) node;

core/src/main/java/com/taobao/arthas/core/command/view/ViewRenderUtil.java

@@ -97,7 +97,7 @@ public class ViewRenderUtil {
                 affectVO.getListenerId()));
 
         if (affectVO.getThrowable() != null) {
-            infoSB.append("\nEnhance error! exception: " + affectVO.getThrowable());
+            infoSB.append("\nEnhance error! exception: ").append(affectVO.getThrowable());
         }
         infoSB.append("\n");
 

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

@@ -91,9 +91,9 @@ public class UserStatUtil {
         public void appendQueryData(String key, String value) {
             if (key != null && value != null) {
                 if (queryData.length() == 0) {
-                    queryData.append(key + "=" + value);
+                    queryData.append(key).append("=").append(value);
                 } else {
-                    queryData.append("&" + key + "=" + value);
+                    queryData.append("&").append(key).append("=").append(value);
                 }
             }
         }

core/src/main/java/com/taobao/arthas/core/util/affect/EnhancerAffect.java

@@ -144,7 +144,7 @@ public final class EnhancerAffect extends Affect {
                 cost(),
                 listenerId));
         if (this.throwable != null) {
-            infoSB.append("\nEnhance error! exception: " + this.throwable);
+            infoSB.append("\nEnhance error! exception: ").append(this.throwable);
         }
         return infoSB.toString();
     }