Multithreading: High-Performance Java

Java was built for multithreading from day one. In modern dev, we rarely manage Thread objects directly; we use the Executor Framework.

The Thread Lifecycle

Threads move from NEW -> RUNNABLE -> BLOCKED/WAITING -> TERMINATED. Context switching between threads is expensive, which is why we use Thread Pools.

The ExecutorService

The ExecutorService abstracts thread management. It maintains a pool of workers and a queue of tasks.

java code
ExecutorService executor = Executors.newFixedThreadPool(10);
executor.submit(() -> {
    System.out.println("Processing async task in " + Thread.currentThread().getName());
});

Synchronization and Volatile

• Synchronized: Ensures only one thread can access a block of code at a time (intrinsic lock).
• Volatile: Ensures variable updates are visible to all threads immediately by bypassing the local CPU cache.

CompletableFuture (Java 8+)

Used for writing non-blocking code. It allows you to chain async operations.

java code
CompletableFuture.supplyAsync(this::fetchData)
    .thenApply(this::processData)
    .thenAccept(System.out::println);

Race Conditions

Always protect shared mutable state with locks or use thread-safe classes from java.util.concurrent.atomic (e.g., AtomicInteger).