[JENKINS-43449] Use @GuardedBy annotation

maven-spy/src/main/java/org/jenkinsci/plugins/pipeline/maven/eventspy/reporter/FileMavenEventReporter.java

@@ -41,6 +41,7 @@
 import java.text.SimpleDateFormat;
 import java.util.Date;
 
+import javax.annotation.concurrent.GuardedBy;
 import javax.annotation.concurrent.ThreadSafe;
 
 /**
@@ -49,7 +50,9 @@
 @ThreadSafe
 public class FileMavenEventReporter implements MavenEventReporter {
     File outFile;
+    @GuardedBy("this")
     PrintWriter out;
+    @GuardedBy("this")
     XMLWriter xmlWriter;
 
     public FileMavenEventReporter() throws IOException {

maven-spy/src/main/java/org/jenkinsci/plugins/pipeline/maven/eventspy/reporter/OutputStreamEventReporter.java

@@ -37,6 +37,7 @@
 import java.nio.charset.StandardCharsets;
 import java.sql.Timestamp;
 
+import javax.annotation.concurrent.GuardedBy;
 import javax.annotation.concurrent.ThreadSafe;
 
 /**
@@ -45,7 +46,9 @@
 @ThreadSafe
 public class OutputStreamEventReporter implements MavenEventReporter {
 
+    @GuardedBy("this")
     final PrintWriter out;
+    @GuardedBy("this")
     final XMLWriter xmlWriter;
 
     public OutputStreamEventReporter(OutputStream out) {