public class SyncThreadTest { public static void main(String arge[]){ final Bank bank = new Bank(); Thread addThread = new Thread(new Runnable() { @Override public void run() { while(true){ try { Thread.sleep(1000); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } bank.addMoney(100); bank.lookMoney(); System.out.println("\n"); } } }); Thread subThread = new Thread(new Runnable() { @Override public void run() { // TODO Auto-generated method stub while(true){ try { Thread.sleep(1000); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } bank.subMoney(100); bank.lookMoney(); System.out.println("\n"); } } }); addThread.start(); subThread.start(); } }