Java Concurrent basic notes

In Java, “async” and “sync” refer to different ways of executing code and handling concurrency.

Synchronous code is executed in a single thread, with each statement being executed in sequence. When a statement is executed, the program waits for it to finish before moving on to the next statement. This can be useful when you need to ensure that certain code is executed in a specific order, but it can be inefficient if the code is doing something that takes a long time to complete, as the program will be blocked until the code finishes.

Asynchronous code, on the other hand, allows multiple tasks to be executed at the same time. Instead of waiting for a task to finish before moving on to the next one, asynchronous code can start a task and then move on to the next one, while the first task is still running in the background. This can be much more efficient, as the program can continue doing other things while waiting for long-running tasks to complete.

In Java, you can write asynchronous code using the CompletableFuture class, which provides a way to execute tasks in the background and then handle the results when they are ready. CompletableFuture allows you to chain together multiple tasks and specify how they should be executed, such as in sequence or in parallel.

To summarize, synchronous code executes one statement at a time in sequence, while asynchronous code allows multiple tasks to be executed in parallel, improving performance and efficiency.

CompletableFuture is a class introduced in Java 8 that provides a way to write asynchronous, non-blocking code. It is a powerful tool for handling complex asynchronous operations in a clear and concise manner.

CompletableFuture is a type of Future that represents a computation that may or may not have completed yet. It can be used to execute a task in the background and then handle the result when it becomes available, or to execute multiple tasks concurrently and then combine the results when they are all ready.

Here are some of the key features of CompletableFuture:

1. Chaining: CompletableFuture allows you to chain together multiple asynchronous operations, so that one operation starts when the previous one finishes. This can be done using methods like thenApply(), thenCompose(), and thenCombine().

2. Combining: CompletableFuture also allows you to combine multiple asynchronous operations into a single operation, using methods like allOf() and anyOf().

3. Error handling: CompletableFuture provides methods for handling errors that may occur during the execution of an asynchronous operation, including exceptionally() and handle().

4. Timeout handling: CompletableFuture allows you to set a timeout for an asynchronous operation, using methods like completeOnTimeout() and orTimeout().

5. Asynchronous execution: CompletableFuture can execute tasks asynchronously on a separate thread, allowing the calling thread to continue with other tasks while the background task is executing.

6. Completion stages: CompletableFuture provides a way to break down complex asynchronous operations into smaller, more manageable stages, using methods like thenApplyAsync(), thenComposeAsync(), and thenAcceptAsync().

Overall, CompletableFuture provides a flexible and powerful way to write non-blocking, asynchronous code in Java, making it easier to handle complex operations and improve performance.