Difference in output from use of synchronized keyword and join()
- by user2964080
I have 2 classes,
public class Account {
private int balance = 50;
public int getBalance() {
return balance;
}
public void withdraw(int amt){
this.balance -= amt;
} }
and
public class DangerousAccount implements Runnable{
private Account acct = new Account();
public static void main(String[] args) throws InterruptedException{
DangerousAccount target = new DangerousAccount();
Thread t1 = new Thread(target);
Thread t2 = new Thread(target);
t1.setName("Ravi");
t2.setName("Prakash");
t1.start();
/* #1 t1.join(); */
t2.start();
}
public void run(){
for(int i=0; i<5; i++){
makeWithdrawl(10);
if(acct.getBalance() < 0)
System.out.println("Account Overdrawn");
}
}
public void makeWithdrawl(int amt){
if(acct.getBalance() >= amt){
System.out.println(Thread.currentThread().getName() + " is going to withdraw");
try{
Thread.sleep(500);
}catch(InterruptedException e){
e.printStackTrace();
}
acct.withdraw(amt);
System.out.println(Thread.currentThread().getName() + " has finished the withdrawl");
}else{
System.out.println("Not Enough Money For " + Thread.currentThread().getName() + " to withdraw");
}
}
}
I tried adding synchronized keyword in makeWithdrawl method
public synchronized void makeWithdrawl(int amt){
and I keep getting this output as many times I try
Ravi is going to withdraw
Ravi has finished the withdrawl
Ravi is going to withdraw
Ravi has finished the withdrawl
Ravi is going to withdraw
Ravi has finished the withdrawl
Ravi is going to withdraw
Ravi has finished the withdrawl
Ravi is going to withdraw
Ravi has finished the withdrawl
Not Enough Money For Prakash to withdraw
Not Enough Money For Prakash to withdraw
Not Enough Money For Prakash to withdraw
Not Enough Money For Prakash to withdraw
Not Enough Money For Prakash to withdraw
This shows that only Thread t1 is working...
If I un-comment the the line saying
t1.join();
I get the same output.
So how does synchronized differ from join() ?
If I don't use synchronize keyword or join() I get various outputs like
Ravi is going to withdraw
Prakash is going to withdraw
Prakash has finished the withdrawl
Ravi has finished the withdrawl
Prakash is going to withdraw
Ravi is going to withdraw
Prakash has finished the withdrawl
Ravi has finished the withdrawl
Prakash is going to withdraw
Ravi is going to withdraw
Prakash has finished the withdrawl
Ravi has finished the withdrawl
Account Overdrawn
Account Overdrawn
Not Enough Money For Ravi to withdraw
Account Overdrawn
Not Enough Money For Prakash to withdraw
Account Overdrawn
Not Enough Money For Ravi to withdraw
Account Overdrawn
Not Enough Money For Prakash to withdraw
Account Overdrawn
So how does the output from synchronized differ from join() ?
