web java /jar code example

Example 1: java load jar at runtime

URLClassLoader child = new URLClassLoader(
        new URL[] {myJar.toURI().toURL()},
        this.getClass().getClassLoader()
);
Class classToLoad = Class.forName("com.MyClass", true, child);
Method method = classToLoad.getDeclaredMethod("myMethod");
Object instance = classToLoad.newInstance();
Object result = method.invoke(instance);

Example 2: run jar file with different jre

First, go to the location of the java installation file. By default, this is:
C:\Program Files\Java\...
Open the folder of the java version you want and go to the bin folder.
Copy the directory your at then go to your command line. 
Syntax: (%PATH% is path you copied):
"%PATH%/java.exe" [javaArgs] [filePath] [yourCodeArgs]