fix #178 by introducing an enum for special allowance of static initializer

agent/src/main/java/reactor/blockhound/BlockHound.java

@@ -99,6 +99,26 @@ private BlockHound() {
 
     }
 
+    /**
+     * Represents special methods that can be used when configuring BlockHound via the {@link Builder}.
+     */
+    public enum TargetType {
+
+        /**
+         * Easily reference the static initializer block of a class.
+         */
+        STATIC_INITIALIZER("<clinit>");
+
+        /**
+         * The {@link String} representation of the special method, as in the JVM specification.
+         */
+        public final String methodName;
+
+        TargetType(String methodName) {
+            this.methodName = methodName;
+        }
+    }
+
     private static final class BlockHoundPoolStrategy implements PoolStrategy {
 
         public static final PoolStrategy INSTANCE = new BlockHoundPoolStrategy();
@@ -289,17 +309,32 @@ public Builder markAsBlocking(String className, String methodName, String signat
 
         /**
          * Allows blocking calls inside any method of a class with name identified by the provided className
-         * and which name matches the provided methodName.
+         * and which name matches the provided methodName. For special methods, use {@link TargetType} instead.
          *
          * @param className class' name (e.g. "java.lang.Thread")
          * @param methodName a method name
          * @return this
+         * @see #allowBlockingCallsInside(String, TargetType)
          */
         public Builder allowBlockingCallsInside(String className, String methodName) {
             allowances.computeIfAbsent(className, __ -> new HashMap<>()).put(methodName, true);
             return this;
         }
 
+        /**
+         * Allows blocking calls inside a special kind of method for a class with name identified by
+         * the provided className. The special method is defined by the provided {@link TargetType}.
+         *
+         * @param className class' name (e.g. "java.lang.Thread")
+         * @param method a {@link TargetType}
+         * @return this
+         * @see TargetType
+         * @see #allowBlockingCallsInside(String, String)
+         */
+        public Builder allowBlockingCallsInside(String className, TargetType method) {
+            return allowBlockingCallsInside(className, method.methodName);
+        }
+
         /**
          * Disallows blocking calls inside any method of a class with name identified by the provided className
          * and which name matches the provided methodName.

example/src/test/java/com/example/StaticInitTest.java

@@ -25,7 +25,7 @@ public class StaticInitTest {
 
     static {
         BlockHound.install(b -> {
-            b.allowBlockingCallsInside(ClassWithStaticInit.class.getName(), "<clinit>");
+            b.allowBlockingCallsInside(ClassWithStaticInit.class.getName(),  BlockHound.TargetType.STATIC_INITIALIZER);
         });
     }