Simple doubt

[Mark Henryson]

class Person{
  
  private Car car;
 
  private String name;
 
  public Car getCar() {
    return car;
  }
 
  public String getName() {
    return name;
  }
 
  public void setName(String s) {
    name = s;
  }
 
  public Person(String s, String t) {
    name = s;
    car = new Car(t);
  }
 
}
 
class Car {
 
  private String name;
 
  public String getName() {
    return name;
  }
 
  public void setName(String s) {
    name = s;
  }
 
  public Car(String s) {
    name = s;
  }
}
 
public class ShallowCopyTest {
 
  public static void main(String[] args) {
    //Original Object
    Person p = new Person("Person-A", "Civic");
    System.out.println("Original (orginal values): " + p.getName() + " - "
        + p.getCar().getName());
  }
}

In the above coding, I have one doubt:

p.getName() --> p is the reference variable holding the Person Object anf thru p we can invoke its method getName();

p.getCar().getName() --> what does this means? How many level of dot we can have. For example: ref-obj.method.??

[Sunil Kumar Gupta]

getCar() method is returning an object
of type car...
U can always use <b>.</b> to call the
methods of this object....

[Mark Henryson]

so, x.y.z means
x - ref variable
y - object
z - method

Any other possibilities??

[Rob Acraman]

p is a reference to a Person object
p.getCar() is a reference to a Car object
p.getCar().getName() is a reference to a String object

In theory, so long as each method returns a reference to an object, you can string any number of "."s together.

In practice, it would be bad coding to put too many - certainly not more than what you've got here. For example, the following clearly does the same :

myCar = p.getCar();
carName = myCar.getName();

However, the advantage with splitting the code like this is it enables debugging and maintenance. You can log the value of myCar to ensure it's what you expected it to be, etc.

[Jim Kiley]

You can have as many "dot" levels as you want. You can, for instance do

String carSubstring = p.getCar().getName().substring(5);

... or whatever else you want.

jk

[Ernest Friedman-Hill]

There is a fairly well known principle called the Law of Demeter which spells out the best practices for using this kind of multi-level access. In short: don't. If you find yourself using multiple dots in an expression, it's a clue that the code you're writing belongs in some other class.