Java 我们什么时候需要实际同步？我的线程是自然同步的

这是我的示例类：我有一个共享对象

CustomerAccount

在两个线程

Man

和

Woman

之间共享。无论何时运行程序，结果都是一致的。为什么会这样

主要类别：

package testjava;

public class PlaywithThreads {

    public static void main(String[] args) throws InterruptedException {
        // TODO Auto-generated method stub
        CustomerAccount ca=new CustomerAccount(0);
        ThreadRunner1 tr1=new ThreadRunner1(ca,"Man");
        ThreadRunner1 tr2=new ThreadRunner1(ca,"Woman");

        tr1.start();
        tr2.start();
        tr1.join();
        tr2.join();
        System.out.println("Final amount left after month"+ca.acctBalance);
    }
}   

螺纹等级：

package testjava;

public class ThreadRunner1 extends Thread{
    private CustomerAccount ca;

    ThreadRunner1 (CustomerAccount ca,String name)
       {

          super (name); 

          this.ca = ca; 
          System.out.println("after this it will create new object");
       }

@Override
public void run() {
    Thread current = Thread.currentThread();
    String name = current.getName();
    System.out.println("Name is"+name);

    // TODO Auto-generated method stub
    if (name.equals("Man")){
        //CustomerAccount caMan = new CustomerAccount();
        /*ca.creditSalary(80000);
        System.out.println(name+""+ca.acctBalance);
        ca.debitFood(8000);

        ca.debitLoans(40000);
        System.out.println(name+""+ca.acctBalance);
        ca.creditBonus(3);

        ca.debitTransport(2000);*/
        ca.acctBalance=ca.acctBalance+80000;
        ca.acctBalance=ca.acctBalance-8000;
        ca.acctBalance=ca.acctBalance-40000;
        ca.acctBalance=ca.acctBalance+3;
        ca.acctBalance=ca.acctBalance-2000;
        System.out.println(name+"----------finally------------"+ca.acctBalance);
    }

    if (name.equals("Woman")){

        //CustomerAccount caWoMan = new CustomerAccount();
        /*ca.creditSalary(50000);
        System.out.println(name+""+ca.acctBalance);
        ca.creditBonus(4);

        ca.debitClothes(20000);


        ca.debitLoans(9000);*/
        ca.acctBalance=ca.acctBalance+50000;
        ca.acctBalance=ca.acctBalance+4;
        ca.acctBalance=ca.acctBalance-20000;
        ca.acctBalance=ca.acctBalance-9000;
        System.out.println(name+"---------Finally-------"+ca.acctBalance);
    }

}
}

共享对象：

package testjava;

public class CustomerAccount {

    int acctBalance;


   // private static int counter;

    public CustomerAccount(int initialBalance) {
        System.out.println("entered");

        this.acctBalance=initialBalance;
        //System.out.println("objects created******************"+counter);
    }
    public void debitFood(int amt){
        System.out.println("debiting food items::for"+Thread.currentThread().getName());
        acctBalance = acctBalance-amt;
        System.out.println("New acct Balance after food debits::"+acctBalance);
    }
    public void debitClothes(int amt){
        System.out.println("debiting clothescost::"+Thread.currentThread().getName());
        acctBalance = acctBalance-amt;
        System.out.println("New acct Balance after clotehs debits::"+acctBalance);
    }
    public void debitTransport(int amt){
        System.out.println("debiting transport::"+Thread.currentThread().getName());
        acctBalance = acctBalance-amt;
        System.out.println("New acct Balance after transport debit::"+acctBalance);
    }
    public void debitLoans(int amt){
        System.out.println("debiting loans::"+Thread.currentThread().getName());
        acctBalance =acctBalance-amt;
        System.out.println("New acct Balance after Loans debit::"+acctBalance);
    }
    public void creditSalary(int salary){
        System.out.println("crediting salary for ::"+Thread.currentThread().getName());
        acctBalance =acctBalance+salary;
        System.out.println("New acct Balance after salary credit::"+acctBalance);
    }
    public void creditBonus(int salary){
        System.out.println("crediting bonus for ::"+Thread.currentThread().getName());
        acctBalance =acctBalance+salary;
        System.out.println("New acct Balance after salary credit::"+acctBalance);
    }
}

---

由于

CustomerAccount

对象是共享的，您应该在那里处理同步。直接成员访问无法做到这一点（从封装的角度来看，这是一个坏主意）。我建议您研究一下

AtomicInteger

作为

acctBalance

的更好类型，它是线程安全的现成工具，但您也可以使

CustomerAccount

的所有方法同步

---

看起来线程是同步的，因为您有很多权限访问synchronizing

System.out.println（）

！如果您删除printf调试并创建更高的负载，您将看到不同的行为。

是的，因为它在两个线程都完成工作后正确地给出了结果。51007这与我从公共余额中添加或减去数量时得到的结果相同。您所说的“我的线程自然同步”是什么意思？从我们的代码中我看到它们不是。代码太简单了，如果您想看到同步的效果，请尝试在

run

方法中添加一个随机等待，例如：

Thread.sleep（Math.ceil（Math.random（）*1000））

很抱歉，这段代码非常糟糕。我建议将其发布到stackoverflow的CodeReview中，以供改进。bashnesnos-这很伤脑筋。我已经删除了println语句，现在我明白了，无论睡眠时间如何，我的操作都会连续进行，并给出相同的结果。我正在考虑创建一个更复杂的操作，以确保它失败。有什么建议吗？