Skip to main content

Public and Private JRE

This one is basic. Newbies in Java are overwhelmed with too many techy terms. Most know JRE, but some find it hard to understand the notation of a Public and Private JRE.

A JRE is nothing but a folder that contains JVM executables, setting files, required lib files, and extensions. You can install multiple JREs on your system Sun generally installs versions in C:\Program Files\Java as jre eg.jre1.6.0_06.

A Public JRE is available to all Java programs, Browsers, and the libs in this JRE folder are available to applications started in command line like
java com.sarathonline.cli.HelloWorld
This JRE is also registered in path, and Browser plugin.

A Private JRE is something that is installed in the system by is not refered to by default. This could be a copy of the JRE / JDK folder from another installed directory. If you see a my earlier post:  starting eclipse with jre 1.6 where your environment is in 1.4, The JRE1.6 is used only by Eclipse, This is a private JRE. While the JAVA_HOME points to 1.4. This is a public JRE.

Why do you need to know this? One situation you would face is the one I explained above. Another example: JRE is not just by Sun, there could be vendor JREs like Weblogic uses JRockit JRE. So you could notice, that a Weblogic server could be started even in a system where java is not installed. Because that is using its own private JRE.

Popular posts from this blog

Javascript: Convert Strings to Binary (and representing in a nerdy way!)

I follow those GoogleDevelopers Videos . Sometime back, in one of the presentations on GoogleIO, there was this interesting string of dots at the bottom of each page of the presentation . They looked like random big and small dots. A similar bunch of dots were also on the T-shirt of a presenter was wearing in another presentation . While it seemed something in the pattern, I could not find what it was. Finally, another presenter cleared the matter that those dots are just binary representation of "GOOGLEIO" (So much for advertizing Google IO, Impressive!). So I wanna do it. Takes me back to days of those DSP classes at school. Nerdy me had to churn some old brain cells. I remember those first programming language classes in Pascal and C when you were asked to do fibonacci series and converting a binary string to ascii codes. That *experience* came handy here: Check it out! Text to Binarize: For those who came to copy the javascript code to convert string to binary,

MySql Copying Table Structures.

Some times you need to copy only table structures across databases. This article describes two ways of doing it. If the whole database schema need to be exported, mysqldump is very effective. A --nodata flag will dump all tables' schema. Like this. mysqldump --nodata -p -u username databaseName But if you want to copy a specific table, individually, you could use "create table like" feature. You could create it even from a different database. However it must be on the same mysqld instance. Like this. create table newtable like oldtable; --Or from a table in other database create table mytable like otherdatabase.tablename;

javascript maxlength for textarea with \r\n breaks in java (esp Firefox)

Textareas allow new lines to enter. These are represented by \n (1) or \r\n (2) characters. But when you save to DB you have a limit to certain length of chars. There is no maxlength attribute in HTML that will stop you from entering data. This is generally acomplished by Javascript. You do a onkeyup hook and stop event or trim after textarea.value.length > maxlength. There are many other solutions out there.. But.. Here is the problem that most of those solutions overlook, How do you deal with the count on \n and \r\n representations. Lets first see how it matters. If the text entered has new lines, the length is calculated differently in Firefox and IE. When you enter a Text like 01234 567890 You expect the textarea.value.length to be 11. (10 chars + new line).On the backend, however, java would recieve it as 12 chars (10 chars + \r\n) (this is irrespective of FF or IE). So you are effectively saving 12 chars to DB. Worse yet, IE seems to figure textarea.value.length as 12 (