I am trying to communicate between two threads which do not share any object in Java (I am building a Java agent). What I need is something like the following :
Thread agentattachThread = ...;
otherThread.send("Hello");
And this would be handled like an interrupt in the Agent Attach thread, like so :
public void msgHandler(String msg) {
...
}
Thread.onMessageReceived(msgHandler);
EDIT - Considering the answers to my original post, my question becomes : does the JVM offer by default a synchronized object to which all threads could get a reference to ?
The only way to "communicate" from thread to thread without sharing some object is via Thread.interrupt() Obviously, the only signal you can send by this means is a true flag, and the receiver will only notice it when it uses certain methods, like Thread.interrupted(), or a method that raises InterruptedException.
Because this is so limited, it's standard practice to share a thread-safe object between threads which offers the interface needed by the application. For example, you could give each thread a reference to the same BlockingQueue and send messages that way.
Any public, static field is globally visible, so a shared object such as a queue could be accessed via such a field by any thread.
The closest thing to that "built-in" to the JVM that comes to mind are system properties; essentially, this is a shared map via which any thread can set or get String-type entries. There might be some other facilities that could be abused in a similar way, but I can't imagine any reason to use something like this when a static field would serve.