What methods can be used to prevent or eliminate deadlocks in a system?

Deadlocks occur when two or more threads or processes wait for each other without releasing resources. To prevent or resolve deadlocks, the following approaches can be used:

1. Avoid cyclic dependencies: always acquire resources in the same order across all threads.

2. Use timeouts when acquiring locks: if a thread cannot obtain a lock within a certain time, it releases already acquired resources and retries.

3. Apply detection and recovery algorithms: periodically check for deadlocks and interrupt or restart one of the threads.

4. Minimize lock holding time: hold locks only for the critical sections of code.

5. Use higher-level synchronization constructs: for example, java.util.concurrent packages, which often implement internal deadlock prevention mechanisms.

Example of ordered lock acquisition:

Object lock1 = new Object();
Object lock2 = new Object();

// Always acquire lock1, then lock2
synchronized(lock1) {
    synchronized(lock2) {
        // critical section
    }
}

If all threads follow this order, deadlocks will not occur.