main() method on Java Exams

main() method on the exam

You can expect to see questions related to the main() method on the certification exam. Make sure that you remember that it has the public and static modifiers and the void return type. Also, remember that its argument is of the String[] type.
You may also be asked a question on how command line arguments are accessed.
Remember that args[0] references the first argument that is passed to the program. This is different from C and C++ programs where args[1] references the first command line argument.

In Java, you need to have a method named main in at least one class.
In the following example, the class Building is being used by the class TestBuilding .

public class Building {
	private int numPeople;

	public Building() {
		numPeople = 0;
	}

	public Building (int initPeople) {
		numPeople = initPeople;
	}
	
	public void setPeople(int peopleSize){	
		numPeople=peopleSize;
	}
	public int getPeople(){
		return numPeople;
	}	
	public String toString() {
		return "Number of people in this building is " + numPeople  + "  ";
	}
}

public class TestBuilding{ 
  public static void main(String [] args){ 
     Building school = new Building(220);  // 220 people in school 
     Building starbucks = new Building(37); 
     Building dentistOffice = new Building(); // default to zero 
     // accessor 
     System.out.println("School: " + school.getPeople() ); 
     // mutator 
     starbucks.setPeople(40); 
     school.setPeople(221); 
     System.out.println("School: " + school.getPeople()); 
     System.out.println("Starbucks: " + starbucks.getPeople()); 
     System.out.println("Dentist: " + dentistOffice.getPeople()); 
 
     // toString 
     System.out.println("Print school, again, but with toString:"); 
     System.out.println( school.toString() );  // explicit toString 
     System.out.println( school );   // implicit toString 
  } 
}