Tag Archives: Udemy

Java Multithreading Notes From Lecture Two

This is part of the notes from an online course (Java Multithreading) I’m taking on Udemy. Nothing complicated.


In theory it is possible that on some system a Java thread may ignore changes to its own data from other threads. If the changes are not made inside its own thread, it may have no effect. We can call it caching variable in thread.

To prevent such thing, we can add the keyword volatile to the variable that may be changed by other threads and guarantee that changes can be seen.

An example on gist.

 

Java Multithreading Notes From Lecture One

This is part of the notes from an online course (Java Multithreading) I’m taking on Udemy. Nothing complicated.


 

There are normally three ways to create threads (Examples on gist):

  • Create a class that extends the Thread class
  • Create a class that implements the Runnable interface
  • Create a Thread anonymously

Whichever we choose to use, we must override or implement the public void run method.

Multithreading:

All Java programs have a main thread, but we can create and invoke other threads from the main thread.

To do that, we need to call the start() method of each thread we want to invoke from main thread. It will look for the run() method and run that in its own special thread, not in the main thread (refer to the App.java in the gist).

The start() method will return immediately so the main thread will continue its execution of the next line of code.

However, if we accidentally call the run() method of those threads, then the method run() will be executed in the main thread, not in its own special thread! So be careful.