Threads - Concepts - Sun Certified Java Programmer 310-065

download the application please visit www.mrbool.com/player

Title: Threads - Concepts - Sun Certified Java Programmer 310-065 - Lesson 40

Duration: 16 minutes

Summary: In this video, we start our discussion of Threads. Thread is a single unit of execution. Threads can be created by extending the Thread class and overriding the run() method. Thread objects can also be created by calling the Thread constructor that takes a Runnable argument. The first questions we tackle help us understand the signature of the methods available, how we can implement the Runnable interface, and the use of the sleep() method. This method has to exist in a try/catch block. Finally, we see how we can synchronize threads. By making the methods as synchronized, the threads will get the lock of the 'this' object before proceeding.

Methodology of the development of example: Good coding standard and simplified design to prepare for the Java programmer certification exam CX-310-065.

Technology Used: Java - Core Concepts.

Keywords: class, object, Thread, start(), run(), Runnable, sleep(), join(), wait(), notify(), notifyAll().

Add a comment!

[Fechar]

Este post é fechado - você precisa ter acesso ao post para incluir um comentário.

Matthew Casperson
4/19/2012 5:53pm

Watch for synchronize on a primitive

This web pages has some good tips on Java Concurrency:

http://tech.puredanger.com/2009/01/28/java-concurrency-bugs-synchronize-object/

In the video for question 4 we are told that the synchronized method as it is presented in option C is incorrect. This is true, but is not explained very well. The issue here is that the synchronized block can not lock on a primitive value, such as an int. Technically, with the way the question is worded, the two private variables held by the class could be Integer objects, like in the class below.

public class Test

{

private Integer a;

private Integer b;

public int read(){synchronized(a){return a+b;}}

public void set(int a, int b){synchronized(a){this.a=a; this.b=b;}}

}

In this configuration, the read() method will work. However, in the set() method, because the synchronized block is locking on "a" as opposed to "this.a", it has to be referring to the int parameter passed in by the method, which means the code is incorrect.

Answer it

Mr.Bool Editor
4/19/2012 7:34pm

RE: Matthew,

send your review to the author of the video, soon, will contact

Answer it

Ayad
4/20/2012 1:25am

RE: Hi Matthew,

Great feedback!

Unfortunately, as I mentioned in the other comment, I did not author the questions. If you notice in the videos I always give credits to the authors and making sure that readers know I did not author these questions.

The idea is that with some background, discussion, and feedback (like we are doing now :) ), readers will grasp the ideas and understand them better.

Keep up the good work.

Ayad

Answer it

Threads - Concepts - Sun Certified Java Programmer 310-065 - Lesson 40 | Java courses

In this video, will see how we can implement the Runnable interface, and the use of the sleep() method.