code: public void setPoolSize(int poolSize) {
          // Assert.isTrue(poolSize > 0, "'poolSize' must be 1 or higher");
          this.poolSize = poolSize;
          if (this.scheduledExecutor instanceof ScheduledThreadPoolExecutor) {
              ((ScheduledThreadPoolExecutor) this.scheduledExecutor).setCorePoolSize(poolSize);
          }
      }
docs: Set the ScheduledExecutorService's pool size. Default is 1.
  <p>
  <b>This setting can be modified at runtime, for example through JMX.</b>
  
  @param poolSize the new pool size