java如何实现静态变量多线程安全问题

问题，如题！
我先说我目前的方案（我感觉不靠谱，但是又不知道如何测试）：

public class SaveDatabasePlanCache {

   private static Integer vehicleSum=0;

    public static Integer getVehicleSum() {
            return vehicleSum;
    }
    
    public synchronized static void  setVehicleSum(Integer vehicleSum) {
        SaveDatabasePlanCache.vehicleSum = vehicleSum;
    }
    
}

测试方案：

        TestThread t1=new TestThread("线程1: ");
        TestThread t2=new TestThread("线程2: ");
        TestThread t3=new TestThread("线程3: ");
        TestThread t4=new TestThread("线程4: ");
        
        ExecutorService service=Executors.newFixedThreadPool(4);
        service.submit(t1);
        service.submit(t2);
        service.submit(t3);
        service.submit(t4);

线程代码：

public void run() {
                int sum=0;
                boolean flag=true;
                while(flag){
                    sum=SaveDatabasePlanCache.getVehicleSum();
                    if(sum==10000){
                        System.out.println(new Date().toLocaleString()+" "+title+"不执行");
                        flag=false;
                    }else{
                        SaveDatabasePlanCache.setVehicleSum(sum+1);
                        System.out.println(new Date().toLocaleString()+" "+title+SaveDatabasePlanCache.getVehicleSum());
                    }
                        
                    
                }
               
            }

上面是我对静态变量的线程安全方案，就是在设置值的时候开启一个线程同步锁的机制，不知道这样是否有效，我在测试的时候，程序死锁过。
请问有什么有效的方法可以测试吗或者解决我当前的问题，谢谢！

---

问题已经解决，我把缓存类的属性改为了原子数据类型代码如下：

    public static AtomicInteger vehicleSum=new AtomicInteger(0);
    public static AtomicInteger vehicleCurrent=new AtomicInteger(1);
    
    public static AtomicInteger vehicle32Sum=new AtomicInteger(0);
    public static AtomicInteger vehicle32Current=new AtomicInteger(1);
    
    public static AtomicInteger vehicle33Sum=new AtomicInteger(0);
    public static AtomicInteger vehicle33Current=new AtomicInteger(1);
    
    public static AtomicInteger vehicleWdSum=new AtomicInteger(0);
    public static AtomicInteger vehicleWdCurrent=new AtomicInteger(1);
    
    public static AtomicInteger vehicleZdSum=new AtomicInteger(0);
    public static AtomicInteger vehicleZdCurrent=new AtomicInteger(1);