fix: WeakReferenceKey.equals NPE (#371)

Author: mr3

README.md

@@ -1,5 +1,5 @@
 [![Build Status](https://github.com/arextest/arex-agent-java/actions/workflows/build.yml/badge.svg?branch=main)](https://github.com/arextest/arex-agent-java/actions/workflows/build.yml)
-[![codecov](https://codecov.io/gh/arextest/arex-agent-java/branch/main/graph/badge.svg)](https://app.codecov.io/gh/arextest/arex-agent-java)
+[![Coverage](https://sonarcloud.io/api/project_badges/measure?project=arextest_arex-agent-java&metric=coverage)](https://sonarcloud.io/summary/overall?id=arextest_arex-agent-java)
 [![Quality Gate Status](https://sonarcloud.io/api/project_badges/measure?project=arextest_arex-agent-java&metric=alert_status)](https://sonarcloud.io/summary/new_code?id=arextest_arex-agent-java)
 
 # <img src="https://avatars.githubusercontent.com/u/103105168?s=200&v=4" alt="Arex Icon" width="27" height=""> AREX

arex-agent-bootstrap/src/main/java/io/arex/agent/bootstrap/InstrumentationHolder.java

@@ -3,9 +3,9 @@
 import java.lang.instrument.Instrumentation;
 
 public class InstrumentationHolder {
-    private static volatile Instrumentation instrumentation;
+    private static Instrumentation instrumentation;
 
-    private static volatile ClassLoader agentClassLoader;
+    private static ClassLoader agentClassLoader;
 
     public static Instrumentation getInstrumentation() {
         return instrumentation;

arex-agent-bootstrap/src/main/java/io/arex/agent/bootstrap/internal/WeakCache.java

@@ -63,9 +63,9 @@ public int hashCode() {
         public boolean equals(Object other) {
             if (other instanceof WeakCache.WeakReferenceKey<?>) {
                 return ((WeakReferenceKey<?>) other).get() == get();
-            } else {
-                return other.equals(this);
             }
+
+            return other != null && other.equals(this);
         }
     }
 }

arex-agent-bootstrap/src/test/java/io/arex/agent/bootstrap/internal/WeakCacheTest.java

@@ -2,6 +2,7 @@
 
 import static org.junit.jupiter.api.Assertions.*;
 
+import java.lang.ref.ReferenceQueue;
 import java.util.concurrent.ForkJoinTask;
 import java.util.concurrent.TimeUnit;
 import org.junit.jupiter.api.AfterEach;
@@ -56,4 +57,11 @@ void testNormalKeyValue() throws InterruptedException {
         // check -> remove after gc
         assertFalse(Cache.CAPTURED_CACHE.contains(null));
     }
+
+    @Test
+    void testWeakReferenceKeyEqualsReturnsFalse() {
+        WeakCache.WeakReferenceKey<String> key = new WeakCache.WeakReferenceKey<>("test", new ReferenceQueue<>());
+        assertFalse(key.equals(null));
+        assertFalse(key.equals("test"));
+    }
 }