I have a simple question about the java classloading mechanism.
I think that the default class loader loads user-defined classes. If I specify other jars in the classpath, does the default classloader go through each jar and load classes from each jar at application startup?
No, it loads classes whenever they are first referenced, either through Class.forName() or through direct use in your code.
Example:
public class First {
static {
System.out.println("first");
}
public static void main(final String[] args) {
System.out.println("second");
Second.third();
}
}
public class Second {
static {
System.out.println("third");
}
public static void third() {
System.out.println("fourth");
}
}
If you run First as a main class, the output is:
first <-- First is loaded
second <-- method in First is executed
third <-- Second is loaded
fourth <-- Method in Second is executed
