title: How can I know at runtime if a JAR file is already in the classpath?
body: <p>What is the best way to know at runtime if a particular JAR file is already in my classpath ? (if that is not the case I should add it at runtime).</p>
  
  <p>I do not know in advance the name of the jar nor the classes in it. A user can select it. The jar represents a runtime plugable component (a driver in my problem).</p>