Invoking a `Runnable` object's `run` method will perform the task in the current thread, not a new oneJAVA-W0135

The run method of the referenced Thread was invoked. Did you mean to invoke start instead?

This code explicitly invokes run on an object. In general, classes implement the Runnable interface because they are going to have their run method invoked in a new thread, in which case Thread.start is the right method to call.

Calling Runnable.run directly will execute code meant to run on a separate thread on the same thread, blocking execution and breaking any code that expects the contents of the run method to be executed on a different thread.

  Thread a = new Thread(new Runnable() {

    @Override
    public void run() { ... }
  });

Bad Practice

  a.run(); // Will not spawn a new thread!

Recommended

  a.start(); // Will spawn a new thread.

  a.join(); // And this works as expected.

References

• Spotbugs - RU_INVOKE_RUN