Concurrency

Analogy: concept

Concurrency is like a Kitchen with Multiple Chefs:

Threads: The chefs working in parallel.
Shared Resource: The single oven they all need to use.
Race Condition: Two chefs trying to put a pizza in the oven at the exact same time (chaos!).
Lock: A rule saying "Only one chef can use the oven at a time".

The Thread Race

Visualize two threads running in parallel and accessing a shared resource.

Concurrency (Thread Race)

Thread 10%

Thread 20%

Shared Resource Value

Without Lock: Threads access the resource chaotically. The final value might be unpredictable (Race Condition).
With Lock: Threads are synchronized. The resource is updated safely.

Key Concepts

Thread: A lightweight unit of execution. A program can have multiple threads running simultaneously.
Race Condition: A bug that happens when multiple threads try to change shared data at the same time. The result depends on who "wins" the race.
Synchronization (Lock): A mechanism to ensure only one thread can access a resource at a time, preventing race conditions.

The Code

class Counter {
    private int count = 0;

    // "synchronized" acts as a Lock
    public synchronized void increment() {
        count++;
    }
}

// Two threads calling increment() at the same time
// Without "synchronized", count might be wrong!