Synchronization

When multiple threads access shared resources (like a variable or file) at the same time, data corruption can occur. This is called a Race Condition.

Synchronization ensures that only one thread accesses the resource at a time.

The synchronized Keyword

You can make a method or a block synchronized.

class Counter {
    private int count = 0;

    public synchronized void increment() {
        count++;
    }
}

If Thread A is inside increment(), Thread B implies wait until A finishes.

Deadlock

Deadlock describes a situation where two or more threads are blocked forever, waiting for each other.

• Thread A holds Resource 1 and waits for Resource 2.
• Thread B holds Resource 2 and waits for Resource 1.

Interactive Code

See a race condition (and try to fix it)!

Quiz

Next Steps

Multithreading is powerful. Now let's jump to Java 8 which introduced modern coding styles.