Question

OK, i need someone to explain to me where to start on this project.

First I need to overload the constructor by adding a default (no-args) constructor to Person that defines an object to have the name “N/A” and an id of -1.

Then i need to add a setter method named reset that can be used to reset the two private instance variables of this class to two values passed in as parameters.

Then I need to add a getter method named getName and getId that can be used to retrieve these two private variables

Here is the code:

public class Person
{
private String name;
private int    id;
private static int personCount = 0;

// constructor
public Person(String pname)
{
name = pname;
personCount++;
id = 100 + personCount;
}



public String  toString()
{
 return "name: " + name + "  id: " + id
  + "  (Person count: " + personCount + ")";
}

// static/class method
public static int getCount()
{
  return personCount;
}

////////////////////////////////////////////////

public class StaticTest
{
  public static void main(String args[])
{
    Person tom = new Person("Tom Jones");
    System.out.println("Person.getCount(): " + Person.getCount());
    System.out.println(tom);
    System.out.println();

    Person sue = new Person("Susan Top");
    System.out.println("Person.getCount(): " + Person.getCount());
    System.out.println(sue);
    System.out.println("sue.getCount(): " + sue.getCount());
    System.out.println();

    Person fred = new Person("Fred Shoe");
    System.out.println("Person.getCount(): " + Person.getCount());
    System.out.println(fred);
    System.out.println();

    System.out.println("tom.getCount(): " + tom.getCount());
    System.out.println("sue.getCount(): " + sue.getCount());
    System.out.println("fred.getCount(): " + fred.getCount());
}
}

I’m not exactly sure where to start and I don’t want just the answer. I’m looking for someone to explain this clearly.

Answer 1

First I need to overload the constructor by adding a default (no-args) constructor to Person that defines an object to have the name “N/A” and an id of -1.

Read about constructors here.

The Person class already contains a ctor that takes 1 argument. What you need to do is create a “default ctor” which is typically a ctor w/out any parameters.

Example:

class x
{
   // ctor w/ parameter
   //
   x(int a)
   {
      // logic here
   }

   // default ctor (contains no parameter)
   //
   x()
   {
     // logic here
   }
}

Then i need to add a setter method named reset that can be used to reset the two private instance variables of this class to two values passed in as parameters.

Setter methods are used to “encapsulate” member variables by “setting” their value via public function. See here.

Example:

class x
{
   private int _number;

   // Setter, used to set the value of '_number'
   //
   public void setNumber(int value)
   {
     _number = value; 
   }
}

Then I need to add a getter method named getName and getId that can be used to retrieve these two private variables

Getters do the opposite. Instead of “setting” the value of a private member variable, they are used to “get” the value from the member variable.

Example:

class x
{
   private int _number;

   // Getter, used to return the value of _number
   //
   public int getNumber()
   {
      return _number;
   }
}

Hope this helps