Java

1. What it is. 2. How to verify that Java threads are kernel-level threads. 2.1. Before running. 2.2. After running.

What Unsafe is, how it relates to manual memory access, and examples of reading and atomically updating fields by memory offset.

After understanding the underlying computer architecture, revisit why the Java Memory Model is needed, what it defines, and happens-before.

1. JVM optimizations for locks: lock elimination, lock coarsening, biased locking, and adaptive locking. 2. Analysis of lock inflation. 3. Application-level optimization of lock usage. 4. Adjusting the number of spins.

Build a simple AQS-like lock by hand to better understand the real AQS source code: requirements, fields, blocking/waking, waiter queue, lock/unlock flow, fairness, final implementation, test, and flow.

A fair lock follows the first-come, first-served principle. Even after the lock has been released, a later-arriving thread cannot barge in; it must wait until nobody is ahead of it. 1. Usage. 2. Principle analysis.

1. What it is. A thread-safe blocking queue. Characteristics: FIFO; blocking insertion when the queue is full and blocking removal when the queue is empty; bounded or unbounded capacity; thread safety. 2. Use cases. Producer-consumer. 3. How to use it. 4. Detailed comparison of BlockingQueue implementations.

1. Usage 2. newCachedThreadPool 3. newScheduledThreadPool 4. newFixedThreadPool 5. newSingleThreadExecutor

1. What it is. A thread-safe HashMap implemented with synchronized + CAS + the HashMap structure (array + linked list + red-black tree). 2. How to use it. 3. Principle analysis: constructor, Node, put, initialization, insertion, resizing, get, remove, and containsKey.

1. Using BlockingQueue. 2. Using wait/notify. 3. Using Lock/Condition. Compared with wait/notify, two Conditions are used so producers and consumers are not woken together; each side wakes only the other side.