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How does this multi-threaded Java code work?

Given this Java code:

class Account {
        private Integer number = 0;
        public synchronized void setNumber(Integer number) {
            this.number = number;
        }

         public synchronized Integer getNumber() {
            return number;
        }
    }

    class Client extends Thread {
        Account account;
        public Client(Account account) {
            this.account = account;
        }
        public  void run() {
            for (int i = 1; i <= 1000; i++) {
            account.setNumber(account.getNumber() + 1);
             }
        }
    }

    public class Run {
        public static void main(String[] args) throws Exception {
            Account account = new Account();
            Client one = new Client(account);
            Client two = new Client(account);
            one.start();
            two.start();
            one.join();
            two.join();
           System.out.println("Exiting main");
       System.out.println("account number value: " +account.getNumber());        
        }
    }

What is the meaning numberwhen the main method is completed? Is it 2000 or less than 2000? I get less than 2000. How can two threads call getNumer()or setNumber()from run()simultaneously, given that each of them is synchronized?

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2 answers

Think about what happens in the next section.

account.setNumber(account.getNumber() + 1);

Although both methods are separately synchronized, the operation as a whole is not.

+8
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2000, . , "set" "get" number , . , "" "increment".

:

number  Thread1     Thread2
0       get => 0    -
-       -           get => 0
-       -           incr => 1
1       -           set => 1
-       incr => 1   -
1       set => 1    -

, , , . , , set/get , .

, Account increment(), get/increment/set , 2000.

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