Java: In this scenario, one thread is waiting for another thread to finish transfer and vice versa. They are stuck with each other, and the program cannot continue. Thus, deadlock occurs. To avoid deadlock it is necessary to lock accounts in the same order. To fix the program we’ll give each account a unique number so that we can lock accounts in the same order when transferring the money. // // DeadlockAccounts.java // public class DeadlockAccounts { public static void main(String[] args) throws InterruptedException { class Account { int balance = 100; public Account(int balance) { this.balance = balance; } public synchronized void deposit(int amount) { balance += amount; } public synchronized boolean withdraw(int amount) { if (balance >= amount) { balance -= amount; return true; } return false; }
Java:
In this scenario, one thread is waiting for another thread to finish transfer and vice versa. They are stuck with each other, and the program cannot continue. Thus, deadlock occurs. To avoid deadlock it is necessary to lock accounts in the same order. To fix the program we’ll give each account a unique number so that we can lock accounts in the same order when transferring the money.
//
// DeadlockAccounts.java
//
public class DeadlockAccounts {
public static void main(String[] args) throws InterruptedException {
class Account {
int balance = 100;
public Account(int balance) { this.balance = balance; }
public synchronized void deposit(int amount) { balance += amount; }
public synchronized boolean withdraw(int amount) {
if (balance >= amount) {
balance -= amount;
return true;
}
return false;
}
public synchronized boolean transfer(Account destination, int amount) {
if (balance >= amount) {
balance -= amount;
synchronized(destination) {
destination.balance += amount;
};
return true;
}
return false;
}
public int getBalance() { return balance; }
}
final Account bob = new Account(200000);
final Account joe = new Account(300000);
class FirstTransfer extends Thread {
public void run() {
for (int i = 0; i < 100000; i++) {
bob.transfer(joe, 2);
}
}
}
class SecondTransfer extends Thread {
public void run() {
for (int i = 0; i < 100000; i++) {
joe.transfer(bob, 1);
}
}
}
FirstTransfer thread1 = new FirstTransfer();
SecondTransfer thread2 = new SecondTransfer();
thread1.start(); thread2.start();
thread1.join(); thread2.join();
System.out.println("Bob's balance: " + bob.getBalance());
System.out.println("Joe's balance: " + joe.getBalance());
} }
Write the deadlock resolved version of the above program.
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