Suppose a bank's ATM machine, which allows users to deposit and withdraw money. Now there is 200 yuan in an account, and both user a and user B have the right to deposit and withdraw money from this a

Suppose a bank ATM machine , It allows users to deposit and withdraw . Now there is a deposit in an account 200 element , user A And the user B Both have the right to deposit and withdraw money from this account . user A Will deposit 100 element , And users B Remove 50 element , Then the final deposit in the account should be 250 element . The actual operation process is as follows ：

(1) to A Deposit operation ：
        1)     Get the deposit amount of the account 200, Time consuming 2s.
        2)     Increase the account amount 100, Time consuming negligible
        3)     The newly generated account result 300 Back to ATM On the server of the machine , Time consuming 2s

(2) Proceed again B Withdrawal operation ： 
        4)     The amount of deposit in the account after being increased 300, Time consuming 2s.
        5)     Judge whether the withdrawal amount is less than the account balance , if , Reduce the account amount 50, Otherwise, an exception will be thrown , Time consuming negligible .
        6)     The newly generated account result 250 Back to ATM On the server of the machine , Time consuming 2s.
     Please according to the above requirements , take A Operation and B The operations of are represented by threads , Write a Java The program realizes this function .

class ATM {
    private float account;

    public ATM(float money) {
        this.account = money;
    }
    public synchronized float getAccount(){
        try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return account;
    }
    public synchronized void deposit(float money){
        account+=money;

    }
    public synchronized void drawMoney(float money) throws Exception {
        if (account < money) {
            throw new Exception(" Lack of balance ");
        }
        account -= money;
    }
}

class UserA extends Thread{
    private ATM atm;
    private float money;
    public UserA(ATM a,float m){
        atm=a;
        money=m;
    }
    public void run(){
        System.out.println(" The amount deposited in the account is ："+atm.getAccount()+" element ");
        System.out.println(" user A Save "+money+" element " );
        try{
            atm.deposit(money);
        }
        catch(Exception e){ }
        System.out.println(" The balance is ："+atm.getAccount()+" element ");
    }
}

class UserB extends Thread{
    private ATM atm;
    private float money;
    public UserB(ATM a,float m){
        atm=a;
        money=m;
    }
    public void run(){
        System.out.println(" The amount deposited in the account is ："+atm.getAccount()+" element ");
        System.out.println(" user B Take out "+money+" element " );
        try{
            atm.drawMoney(money);
            System.out.println(" The balance is ："+atm.getAccount()+" element ");
        }
        catch(Exception e){
            System.out.println(e.getMessage());
        }

    }
}
class TestATM{
    public static void main(String[] args) {
        ATM a=new ATM(200);
        UserA userA=new UserA(a,100);
        UserB userB=new UserB(a,50);
        userA.start();

        try {
            userA.join();// The current thread is blocked , Until the execution of another thread is completed , Unblock current thread 
        } catch (InterruptedException e) {
            userB.start();
        }
        System.out.println("==================");
        userB.start();
        try {
            userB.join();
        } catch (InterruptedException e) {
            userA.start();
        }
    }
}

Running results ：