Building classpath at runtime

23 Jan 2007 18:12:13 -0800
I see this question appearing very often in forums but couldn't find a
satisfactory answer. Following is what I am trying achive
1. I have a java application that depends on several classes that are
packaged as jars.
2. Application runs as java -jar "XXX" -cp <classpath>
3. I sometimes need to create emergency fixes or jars. I will like to
put them in an "updates" directory. As names of these jar files will be
determined later, I want my program to scan "updates" directory at
startup, and prepend (before initial classpath) any discovered jar
4. I know that ClassLoader.loadClass() is a viable method but most of
my code takes a new <class>() approach. I will appreciate any

Following is my sample test code.

//////////////////////////// Sample Code

import java.util.Properties;

public class PropertiesTest {
    public static void main(String[] args) throws Exception {

        // My original classpath does not have c:\\updates
"=c:\\updates;.;C:\\Program Files\\Java\\jre1.5.0_06;c:\\updates");
        NewClass myclass = new NewClass(); // >>>>>>>> Need to load
this class from a location "c:\updates"
         // determined at runtime<<<<

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