source code call garbage collection use some methods

package funds;
class Sam
{
   int i=10;
   String n="java";
}
public class GCRun {
   public static void main(String arg[])
   {
       Sam s=new Sam();
       s=null;
       System.gc();
       Sam s2=new Sam();
       s2=null;
       Runtime r=Runtime.getRuntime();
       r.gc();
   }

}