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Trace how Java runs one statement, enters a method call, returns, and then moves to the next line. You will use this single path of execution as the baseline for every later thread-pool idea.
Use what you learned in the previous lesson to solve real-world problems.
Distinguish writing code from actually running work. You will see that a method, lambda, Runnable, or Callable is only a recipe until some execution path invokes it.
Check what you understood with a short quiz.
Turn a small piece of Java work into a task with a clear boundary. You will compare Runnable for “do this” work with Callable for work that produces a value or reports failure.
Reason through why a slow line delays everything after it on the same path. You will connect file I/O, network calls, database calls, and sleep to the simple rule: the next step waits.
Recognize when a program is doing useful work versus sitting blocked for something else. You will label common waits, such as input, locks, timers, and external services, without treating waiting as progress.
Predict what changes when work is handed to another path of execution. You will separate “I asked for work to start” from “the work has finished,” which is the key timing gap behind concurrency.
Compare sequential order with concurrent order. You will see why two independent paths may print, finish, or fail in different orders from run to run, even when the code is unchanged.
Identify resources that multiple tasks can touch, such as variables, collections, files, logs, sockets, and database rows. You will mark which effects are private to one task and which could collide with other work.
Use task names, thread names, and timestamps in log messages to reconstruct what happened. You will practice reading output without assuming that nearby log lines came from the same path of execution.
Choose when one-at-a-time execution is the right model. You will reason about cases where simple sequential code is clearer and safer than splitting work before there is a real need.
Review this chapter with practice based on your mistakes.
