Coding style and organization

Question

So I am currently making a airplane reservation system for a summer project to keep fresh with Java. With any reservation system its requiring a lot of classes and methods. Currently I'm working on importing the fleet.

My main method is acting like the chronological guide to my program.

public static void main(String[] args){
    //start here 
    //accept passenger credentials 
    //place passenger in seat on plane
}

My question is a formatting problem. When I'm looking to start "making" my aircraft for my fleet. It goes a little like this.

//...
Airplane Boeing737 = new Airplane(seats[], nameOfAircraft);

This will put all values that i need to construct my airplane, obviously there are more variables for the airplane constructor.

My thought is to make a method in the Airplane class that will do this for me. but in order to do this i need to call a blank constructor for the other class (the one with my main method) to see it. I feel like this is horrible form for some reason. Is there a better way to do this?

Another thought as I'm posting is to modify the constructor to not accept any arguments and have that do everything in there. I feel like that's what I should be doing but I'm not 100% sure that would be the correct choice. I guess my overall question would be what are best practices in situations like this.

Answer 1

Use builder pattern, this will allow you:

• dynamic way of building events
• maintainable code (you can add more params when you want)
• preserve integrity of the objects when created

---

Joshua Bloch's in Effective Java Chapter 1 Item 2 states:

Luckily, there is a third alternative that combines the safety of the telescoping constructor pattern with the readability of the JavaBeans pattern. It is a form of the Builder pattern. Instead of making the desired object directly, the client calls a constructor (or static factory) with all of the required parameters and gets a builder object.

Modifying his example:

//Builder Pattern
public class Airplane  {
    private final int[] seats;
    private final String name;
    private final int maxSpeed;
    private final int maxPassengers;

    public static class Builder {
        // Required parameters
        private final int[] seats;
        private final String name;

        // Optional parameters - initialized to default values
        private int maxSpeed = 1000;
        private int maxPassengers = 150;

        public Builder(int[] seats, String name) {
            this.seats = seats;
            this.name = name;
        }

        public Builder maxSpeed(int val) {
            maxSpeed = val;
            return this;
        }

        public Builder maxPassengers(int val) {
            maxPassengers = val;
            return this;
        }

        public Airplane build() {
            return new Airplane(this);
        }
    }

    private Airplane(Builder builder) {
        seats = builder.seats;
        name = builder.name;
        maxSpeed = builder.maxSpeed;
        maxPassengers = builder.maxPassengers;
    }
}

Then you can create several different airplanes

public static void main(String[] args) {
    // only mandatory params
    Airplane boeing747  = new Airplane.Builder(new int[] {1,0,1}, "boeing747").build();
    // just one param
    Airplane boeing646  = new Airplane.Builder(new int[] {1,1,1}, "boeing646").maxPassengers(250).build();
    // all params
    Airplane fighter    = new Airplane.Builder(new int[] {1,0,0}, "fighter_1").maxPassengers(3).maxSpeed(1600).build();
}