Chaining multiple constructors

A constructor is up to set as many fields as possible or construct an instance completely.

You pick a constructor which has a greater number of arguments and use it within constructors with a smaller amount. For example,

public Flight(double maxKgPerPassenger) { this(0, 0, maxKgPerPassenger); // default, default, maxKgPerPassenger } private Flight(int passengers, int seats, double maxKgPerPassenger) { this.passengers = passengers; this.seats = seats; this.maxKgPerPassenger = maxKgPerPassenger; } 

I want to chain to all constructors so that they can all be private other than the main constructor.

I suggest the opposite way. Make all constructors you are going to use public, but an all-arguments constructor private if you won't be using that.

The approach you tried to adopt is similar to the builder pattern where each method sets a single field. You definitely need to have a look at it if a number of arguments are going to grow up.

Why do you want to chain constructors ?
As you chain constructors, you have to specify some default values from the constructor with less argument to the invoked constructor with more arguments.
You do the reverse here :

public Flight(int passengers, int seats, double maxKgPerPassenger){ this(passengers); this(seats); this(maxKgPerPassenger); } 

You indeed want to invoke from the constructor with the most argument all other constructors.
It makes no sense and it is not valid either as a constructor can invoke a single other constructor of the same class.

I want to chain to all constructors so that they can all be private other than the main constructor.

Things work in the reverse order.

The actual code doesn't seem to need constructor chaining.
This one is enough :

public Flight(int passengers, int seats, double maxKgPerPassenger){ this.passengers = passengers; this.seats = seats; this.maxKgPerPassenger = maxKgPerPassenger; } 

Suppose that class clients could create Flight instances with two flavors :

• by passing all parameters
• by passing only the seats parameter (remains being valued with default values)

You could so write :

public Flight(int passengers, int seats, double maxKgPerPassenger){ this.passengers = passengers; this.seats = seats; this.maxKgPerPassenger = maxKgPerPassenger; } public Flight(int seats){ super(50, seats, 10); // you pass some default values for passengers and maxKgPerPassenger } 

make the default constructor private to prevent constructor instantiation and instantiate objects using a public static method. This way you can work around the constructor restriction. To add a little confusion I converted your constructors to normal methods using the class name by adding void return type. Also consider if want you really want isn't the Builder pattern.

 public class Flight { private int passengers = 0; private int seats = 150; private double maxKgPerPassenger; private Flight() {} private void Flight(int passengers) { this.passengers = passengers; } private void Flight(int seats) { this.seats = seats; } private void Flight(double maxKgPerPassenger) { this.maxKgPerPassenger = maxKgPerPassenger; } public static Flight create(int passengers, int seats, double maxKgPerPassenger) { Flight flight = new Flight(); flight.Flight(passengers); flight.Flight(seats); flight.Flight(maxKgPerPassenger); return flight; } }