What methods can be used to implement a sequence of tasks or operations?

In Java, there are several approaches to organize sequential execution of tasks or operations:

1. Sequential method calls — the simplest way, where one operation is called after another in the desired order.

2. Using threads with synchronization — if tasks are executed in different threads, methods like join(), wait()/notify(), CountDownLatch, CyclicBarrier can be used to order execution.

3. ExecutorService and Future — with a thread pool, tasks can be launched and their completion awaited using Future objects, allowing control over the sequence.

4. CompletableFuture — a modern way of asynchronous programming, enabling chaining of tasks using methods like thenApply(), thenCompose(), etc.

5. Chain of Responsibility pattern — for sequential processing of data or events through a chain of handlers.

Example of using CompletableFuture for sequential execution:

CompletableFuture.supplyAsync(() -> {
    // first task
    return "Result 1";
}).thenApply(result -> {
    // second task using the result of the first
    return result + " and Result 2";
}).thenAccept(finalResult -> {
    System.out.println(finalResult);
});