20165230 2017-2018-2 "Java Programming" 8th Week study Summary

20165230 2017-2018-2 "Java Program Design" 8th Week study Summary Textbook Learning contents Summary 12th Chapter Java Multithreading mechanism

• A process can produce multiple threads during its execution. A thread is a smaller execution unit than a process
• The JVM guarantees that each thread will have the opportunity to use CPU resources until all threads in the Java application end before ending the application

Thread state and life cycle

• Using Thread objects of classes and their subclasses to represent threads
• Invokes start() a method to join a thread to the JVM management queue. The call can no longer be called by the thread to the start() method
• run()METHOD specifies the specific mission of the thread. The thread becomes a dead state after the method has finished executing.
  - sleep(int millsecond) puts the thread into hibernation. A thread with high priority can let the CPU resources be executed with a low priority thread
• wait()method causes the thread to enter a wait state. notify()The method enables the thread to continue running from the point of interruption. The method is usually wait() put into a "while" loop statement

Common methods

• isAlive()Used to determine if a thread is in a new state or into a dead state, and if so, returns false.
• A thread that is already running does not assign an entity to a thread when it does not enter a dead state
• currentThread()Returns the thread that is currently using CPU resources

• interrupt()The thread used to "wake up" the calling sleep() method to hibernate

  Thread class and threading creation
• When writing subclasses, you need to override the run() method

• To create a thread constructor: Thread(Runnable target) The parameter is an interface of type runnable, passing an instance object to the interface

  Thread synchronization
• Thread synchronization mechanism: When a thread uses a synchronized method, other threads must wait with the method if they want to use it wait() until the thread finishes using the method
• While other threads do not need to wait while using the synchronous method, the execution notifyAll() method notifies all waiting threads to end the wait while the method is exhausted

• You cannot use the wait (), notify (), Notifyall () methods in a non-synchronous method

  Thread Federation

• The b thread is available through the B.join() federated a thread. A thread will break execution immediately and resume execution when B is finished

  GUI thread
• Awt-eventquecue thread is responsible for handling GUI events

• Awt-windows thread is responsible for drawing a form or component to the desktop

  Timer thread
• Timer(int a,Object b)Create a Timer
• start()Start timer
• stop()Stop Timer

• restartRestart Timer

  Daemon Threads
• Invoke void setDaemon(boolean on) method Settings Daemon Thread

• A thread must set itself as a daemon before running

  Problems in teaching materials learning and the solving process
• Question 1: What is the difference between the two ways to implement Java multi-threading?

• Issue 1 Resolution: Learn through Blogs

  Inherited thread classes are used:

  • (1) Advantages: Write simple, if you need to access the current thread, without using the Thread.CurrentThread () method, use this directly, you can get the current thread.
  • (2) Cons: Because the thread class has inherited the thread class, it is no longer possible to inherit other parent classes.
  • Implement the Runnable interface method:
  • (1) Advantages: The threading class simply implements the Runable interface and can inherit other classes. In this way, multiple threads can share the same target object, so it is very suitable for multiple identical threads to handle the same resource, so that the CPU code and data can be separated to form a clear model, which is a good embodiment of object-oriented thinking.
  • (2) Cons: Programming is slightly more complex, if you need access to the current thread, you must use the Thread.CurrentThread () method.

• Question 2:p377 in the code tickethouse why wait() change Thread.sleep(3000) , Li Kui can never buy tickets?

• Issue 2 Resolved: By comparing the Wait () method and the thread () method, you learned:

  During the call to the sleep () method, the thread does not release the object lock.
  When the Wait () method is called, the thread discards the object lock, enters the waiting lock pool waiting for the object, and the thread only enters the object lock pool when the Notify () method is called for this object.
  Gets the object lock into the running state.

Problems in code debugging and the resolution process

• Question 1: When debugging the Example12_3, why the result is the dog drink 7 left, the cat drink 8?
• Issue 1: Through the learning materials video learned that each computer's running results are not the same, the output of the current CPU resource usage depends on

Last week's summary of the wrong quiz

• Wrong question 1
  

• Select is also the data manipulation language

• Wrong question 2
  

• The book said: "Directly shut down the MySQL database server occupied by the command line window cannot shut down the MySQL database server, you can use Task Manager to close the"

Code Hosting

Https://gitee.com/BESTI-IS-JAVA-2018/20165230/commit/5dd42538867b45b2b037b6d2039c2cf622fd26d9

Code

Learning progress Bar

	lines of code (new/cumulative)	Blog Volume (Add/accumulate)	Learning Time (new/cumulative)	Important Growth
Goal	5000 rows	30 Articles	400 hours
First week	13/13	1/30	19/19
Second week	426/426	3/30	12/12
Third week	562/562	4/30	15/15
Week Four	1552/1958	5/30	16/16
Week Five	1123/3086	6/30	14/14
Week Six	747/3833	8/30	12/12
Seventh Week	953/4786	11/30	13/3
Eighth Week	4564/5881	13/30	14/14

Resources

• "Java2 Practical Course (Fifth Edition)" Learning Guide

• Comparison of two methods of Java multithreading

• The difference between sleep () and wait () in Java

• Intellj Idea Easy Tutorial

20165230 2017-2018-2 "Java Programming" 8th Week study Summary