[jboss-jira] [JBoss JIRA] (JBCOMMON-126) NullPointerException when using PropertyMap concurrently

NullPointerException when using PropertyMap concurrently -------------------------------------------------------- Key: JBCOMMON-126 URL: https://issues.jboss.org/browse/JBCOMMON-126 Project: JBoss Common Issue Type: Bug Security Level: Public(Everyone can see) Components: common-core (2.x) Affects Versions: 2.2.18.GA Environment: All environments Reporter: Michael Pradel Assignee: Dimitris Andreadis Fix For: 2.2.20.GA PropertyMap extends Properties, which is a thread-safe class, but it doesn't preserve its thread safety. This leads to surprising crashes if you have a reference of type Properties (documented as thread-safe) that turns out to be a PropertyMap (not thread-safe). Here's a simplified example that shows how we hit this bug: final Properties p = getProps(); p.setProperty("a", "b"); Thread t1 = new Thread(new Runnable() { public void run() { p.remove("a"); } }); Thread t2 = new Thread(new Runnable() { public void run() { p.clear(); } }); t1.start(); t2.start(); try { t1.join(); t2.join(); } catch (InterruptedException e) { e.printStackTrace(); } Properties getProps() { // return new Properties(); // OK return new PropertyMap(); // leads to NullPointerException } The code runs fine if getProps returns Properties (as it should, because Properties is thread-safe), but raises a NullPointerException if getProps returns a PropertyMap. Are you aware of this inconsistency? It seems that the safest way of extending Properties is to make methods that override synchronized methods synchronized.