--- old/src/java.base/share/classes/java/lang/ThreadLocal.java	2018-06-06 20:45:07.137552986 +0200
+++ new/src/java.base/share/classes/java/lang/ThreadLocal.java	2018-06-06 20:45:07.038554668 +0200
@@ -24,6 +24,8 @@
  */
 
 package java.lang;
+import jdk.internal.misc.TerminatingThreadLocal;
+
 import java.lang.ref.*;
 import java.util.Objects;
 import java.util.concurrent.atomic.AtomicInteger;
@@ -171,6 +173,19 @@
     }
 
     /**
+     * Returns {@code true} if there is a value in the current thread's copy of
+     * this thread-local variable, even if that values is {@code null}.
+     *
+     * @return {@code true} if current thread has associated value in this
+     *         thread-local variable; {@code false} if not
+     */
+    boolean isPresent() {
+        Thread t = Thread.currentThread();
+        ThreadLocalMap map = getMap(t);
+        return map != null && map.getEntry(this) != null;
+    }
+
+    /**
      * Variant of set() to establish initialValue. Used instead
      * of set() in case user has overridden the set() method.
      *
@@ -184,6 +199,7 @@
             map.set(this, value);
         else
             createMap(t, value);
+        TerminatingThreadLocal.register(this);
         return value;
     }