非同步方法可以被其他线程访问

Question

The lock on an object by one thread, no other thread can enter any of the synchronized methods in that class ,but i want to know about non-synchronized method can access by other thread,,,,,,,

class Account {

    private int balance = 50;

    public int getBalance() {
        return balance;
    }

    public void withdraw(int amount) {
        balance = balance - amount;
    }
}

public class AccountDanger implements Runnable {

    private Account acct = new Account();

    public void run() {
        for (int x = 0; x < 5; x++) {
             this. d();
            makeWithdrawal(10);

            if (acct.getBalance() < 0) {
                System.out.println("account is overdrawn!");
            }
        }
    }

    private synchronized void  makeWithdrawal(int amt) {
        if (acct.getBalance() >= amt) {
            System.out.println(Thread.currentThread().getName()
                    + " is going to withdraw"+amt);
            try {
                Thread.sleep(500);
               // Thread.sleep(500);

            } catch (InterruptedException ex) {
            }
            acct.withdraw(amt);
            System.out.println(Thread.currentThread().getName()
                    + " completes the withdrawal"+acct.getBalance());
        } else {
            System.out.println("Not enough in account for " + Thread.currentThread().getName()
                    + " to withdraw " + acct.getBalance());
        }
    }

    public static void main(String[] args) {
        AccountDanger r = new AccountDanger();
        Thread one = new Thread(r);
        Thread two = new Thread(r);
        one.setName("Fred");
        two.setName("Lucy");
        one.start();
        two.start();
    }

    private void d() {
        System.out.println("hhhhhhhhhhhhhhhhhhhhh"+Thread.currentThread().getName());
    }

}

Answer 1

You have answer in your question itself :). If you are just looking for confirmation : YES.

No lock is required to access non-synchronized methods of an object.

If you want to know more about these concepts, visit Object Locks

Answer 2

Yes, the unsynchronized methods can be accessed/called by any Thread, that has/gets the reference to the same instance. Since you created a private Account instance and you didn't give this instance to any other class, in your example no other thread is able to access this special instance.