The Premain class will contain the method "premain(String agentArgs Instrumentation inst)"
Here is an example:
import java.lang.instrument.Instrumentation;
public class PremainExample {
public static void premain(String agentArgs, Instrumentation inst) {
System.out.println(agentArgs);
}
}
When compiled into a jar file open the Manifest and ensure that it has the Premain-Class attribute.
Here is an example:
Premain-Class: PremainExample
To use the agent with another java program "myProgram" you must define the agent in the JVM arguments:
java -javaagent:PremainAgent.jar -jar myProgram.jar