the static paramater is best to be referenced by the class (#2868)

* fix potential NullPointerException

* Revert "fix potential NullPointerException"

This reverts commit 8393656

* fix potential NullPointerException
the static paramater is best to use the class to reference

oap-server/server-receiver-plugin/envoy-metrics-receiver-plugin/src/main/java/org/apache/skywalking/oap/server/receiver/envoy/als/K8sALSServiceMeshHTTPAnalysis.java

@@ -175,7 +175,7 @@ public class K8sALSServiceMeshHTTPAnalysis implements ALSHTTPAnalysis {
                 if (request != null) {
                     endpoint = request.getPath();
                     String schema = request.getScheme();
-                    if (schema.equals("http") || schema.equals("https")) {
+                    if ("http".equals(schema) || "https".equals(schema)) {
                         protocol = Protocol.HTTP;
                     } else {
                         protocol = Protocol.gRPC;
@@ -278,7 +278,7 @@ public class K8sALSServiceMeshHTTPAnalysis implements ALSHTTPAnalysis {
                 if (request != null) {
                     endpoint = request.getPath();
                     String schema = request.getScheme();
-                    if (schema.equals("http") || schema.equals("https")) {
+                    if ("http".equals(schema) || "https".equals(schema)) {
                         protocol = Protocol.HTTP;
                     } else {
                         protocol = Protocol.gRPC;

oap-server/server-receiver-plugin/skywalking-trace-receiver-plugin/src/main/java/org/apache/skywalking/oap/server/receiver/trace/provider/parser/SegmentParse.java

@@ -275,7 +275,7 @@ public class SegmentParse {
             segmentParse.setStandardizationWorker(standardizationWorker);
             boolean parseResult = segmentParse.parse(bufferData, Source.Buffer);
             if (parseResult) {
-                segmentParse.TRACE_BUFFER_FILE_OUT.inc();
+                TRACE_BUFFER_FILE_OUT.inc();
             }
 
             return parseResult;

oap-server/server-receiver-plugin/skywalking-trace-receiver-plugin/src/main/java/org/apache/skywalking/oap/server/receiver/trace/provider/parser/SegmentParseV2.java

@@ -275,7 +275,7 @@ public class SegmentParseV2 {
             segmentParse.setStandardizationWorker(standardizationWorker);
             boolean parseResult = segmentParse.parse(bufferData, SegmentSource.Buffer);
             if (parseResult) {
-                segmentParse.TRACE_BUFFER_FILE_OUT.inc();
+                TRACE_BUFFER_FILE_OUT.inc();
             }
 
             return parseResult;