What Is an Object?

public class GymMember {
    public String name;
    public Integer age;
}

GymMember member1 = new GymMember();
member1.name = 'Zanele';
member1.age = 28;

1. public class GymMember { — the blueprint, same as the previous lesson.
2. public String name; — a field for the name.
3. public Integer age; — a field for the age.
4. } — closes the class.
5. (blank line)
6. GymMember member1 = new GymMember(); — new GymMember() builds one actual object from the blueprint, and member1 is a variable holding a reference to it.
7. member1.name = 'Zanele'; — fills in that specific object's name.
8. member1.age = 28; — and its age.

GymMember member1 = new GymMember();
member1.name = 'Zanele';

GymMember member2 = new GymMember();
member2.name = 'Kofi';

System.debug(member1.name); // Zanele
System.debug(member2.name); // Kofi

1. GymMember member1 = new GymMember(); — creates the first object.
2. member1.name = 'Zanele'; — sets its name.
3. (blank line)
4. GymMember member2 = new GymMember(); — creates a second, completely separate object.
5. member2.name = 'Kofi'; — sets the second object's name — this has no effect on member1.
6. (blank line)
7. System.debug(member1.name); — logs Zanele.
8. System.debug(member2.name); — logs Kofi.

member1 and member2 are both GymMember objects, built from the same class, but changing one never affects the other — exactly like two houses built from the same blueprint don't share walls.

• Forgetting new. GymMember member1; declares a variable that can hold a GymMember, but it starts out null — no object exists until new GymMember() actually creates one.
• Assuming two variables always mean two objects. GymMember member3 = member1; doesn't create a new object — member3 and member1 both point to the same object, so changing one through either variable affects both.