请看这段代码(摘自《EffectiveJava》一书)importjava.util.concurrent.TimeUnit;publicclassMain{privatestaticbooleanstopReq;publicstaticvoidmain(String[]args)throwsInterruptedException{Threadbgw=newThread(newRunnable(){publicvoidrun(){inti=0;while(!stopReq){i++;}}});bgw.start();TimeUnit.SECONDS.sleep(1);stopReq=