This can be done using the static block of the class. The static initialization blocks get executed as soon as the class is loaded, even before the main method is called. During run time JVM will search for the main method after exiting from this block. If it does not find the main method, it throws an exception. To avoid the exception system.exit (0); statement is used which terminates the program at the end of the static block itself.

class Example
{
static
{
System.out.println("hi");
System.exit(0);

}
}