refactor access specifiers

Author: Naman Nandan

frontend/server/src/main/java/org/pytorch/serve/metrics/MetricCollector.java

@@ -20,12 +20,12 @@
 public class MetricCollector implements Runnable {
 
     private static final Logger logger = LoggerFactory.getLogger(MetricCollector.class);
+
+    private static final MetricCache METRIC_CACHE = MetricCache.getInstance();
     private ConfigManager configManager;
-    private MetricCache metricCache;
 
     public MetricCollector(ConfigManager configManager) {
         this.configManager = configManager;
-        this.metricCache = MetricCache.getInstance();
     }
 
     @Override
@@ -79,15 +79,15 @@ public void run() {
                     if (metric == null) {
                         logger.warn("Parse metrics failed: " + line);
                     } else {
-                        if (this.metricCache.getMetricFrontend(metric.getMetricName()) != null) {
+                        if (METRIC_CACHE.getMetricFrontend(metric.getMetricName()) != null) {
                             try {
                                 List<String> dimensionValues = new ArrayList<String>();
                                 for (Dimension dimension : metric.getDimensions()) {
                                     dimensionValues.add(dimension.getValue());
                                 }
                                 // Frontend metrics by default have the last dimension as hostname
                                 dimensionValues.add(metric.getHostName());
-                                this.metricCache
+                                METRIC_CACHE
                                         .getMetricFrontend(metric.getMetricName())
                                         .addOrUpdate(
                                                 dimensionValues,

frontend/server/src/main/java/org/pytorch/serve/wlm/WorkerLifeCycle.java

@@ -238,7 +238,7 @@ private static final class ReaderThread extends Thread {
                 Pattern.compile("^(INFO > )?(\\[PID])(\\d+)$");
         private static final Logger loggerModelOutput =
                 LoggerFactory.getLogger(ConfigManager.MODEL_LOGGER);
-        private final MetricCache metricCache;
+        private static final MetricCache METRIC_CACHE = MetricCache.getInstance();
         private InputStream is;
         private boolean error;
         private WorkerLifeCycle lifeCycle;
@@ -249,7 +249,6 @@ public ReaderThread(String name, InputStream is, boolean error, WorkerLifeCycle
             this.is = is;
             this.error = error;
             this.lifeCycle = lifeCycle;
-            this.metricCache = MetricCache.getInstance();
         }
 
         public void terminate() {
@@ -270,14 +269,14 @@ public void run() {
                         logger.info("result={}, pattern={}", result, matcher.group(2));
                         Metric parsedMetric = Metric.parse(matcher.group(3));
                         if (parsedMetric != null) {
-                            if (this.metricCache.getMetricBackend(parsedMetric.getMetricName())
+                            if (METRIC_CACHE.getMetricBackend(parsedMetric.getMetricName())
                                     != null) {
                                 try {
                                     List<String> dimensionValues = new ArrayList<String>();
                                     for (Dimension dimension : parsedMetric.getDimensions()) {
                                         dimensionValues.add(dimension.getValue());
                                     }
-                                    this.metricCache
+                                    METRIC_CACHE
                                             .getMetricBackend(parsedMetric.getMetricName())
                                             .addOrUpdate(
                                                     dimensionValues,