Why wait(), sleep(), notify(), notifyAll() must be inside a synchronized block,

  Click here to read full story

Question: Why wait(), sleep(), notify(), notifyAll() must be inside a synchronized block, otherwise it throws java.lang.IllegalMonitorStateException: current thread not owner.

Answer: Wait/notify unlocks the monitor and it is not synchronized another thread can try to access it and start a race condition.
*******************************************
 

Java Code Examples for the Thread class

88 comments |    | Score: 3.5

If I run my applet with the SUN VM I get exception: ''Either ''code'' or ''objec

  Click here to read full story

Question: If I run my applet with the SUN VM I get exception: "Either "code" or "object" should be specified, but not both." It does not happen with the Microsoft VM.

Answer: I found good recommendations on Sun’s website about how to install latest browsers and avoid possible problems with running applets in different browsers:
"This is a compatibility issue. To avoid the exception with the Sun VM, do not use an attribute named object with the PARAM element in an applet.
For Netscape 7, or Mozilla 1.1 or later, running on Microsoft Windows, the browser will always use Sun's latest JRE—even if you have deselected the "Netscape 6 or later" or "Mozilla 1.1 or later" check box in the Browser tab of the Java Plug-in Control Panel. This is due to the auto-scan features of these browsers. For instance, if Netscape 7 is installed on a Windows machine that has Sun's 1.4.2 JRE installed as the latest version and you deselect "Netscape 6 or later" in the Control Panel, Netscape 7 will still run Sun's 1.4.2 JRE (Java Plug-in).

Using Java Plug-in 1.4.2 in conjunction with Netscape TM 6.x browsers can cause erratic behavior, including closure of the browser window, for applets that invoke applet functions from JavaScript. This problem is due to a bug in the browser, and you can avoid this problem by using Netscape 7.0 browsers.

The Netscape 7 installer provides three choices for installation: Recommended, Full, and Custom. The Java Plug-in may not work properly in Recommended or Full installations of Netscape 7 browsers. Such Netscape 7 browsers may close when attempting to launch an applet. To avoid this problem, install Netscape 7 using the Custom option, and choose not to install the Quality Feedback Agent.

When installing Java Plug-in, it is necessary to shut down and then restart your web browser. On Microsoft Windows platforms, Netscape 7 has a Quick Launch feature that keeps it running in the background so that it can be launched with minimal start-up time from a Quick Launch icon in the system tray. To completely shut down Netscape 7, you must exit Netscape 7 from its Quick Launch icon in the system tray. "

This tip is based on:
http://java.sun.com/j2se/1.4.2/relnotes.html#vm


31 comments |    | Score: 5