CODEWITHSUNDEEP
javacopy-constructoroptional-parameters
user1347096
user1347096

Reputation: 165

copy constructor in java

class Client{
private String name;
private int age;
private int amount;
public Client(Client otherClient){
    name=otherClient.name;
    age=otherClient.age;
    amount=otherClient.amount;
    }
}

What if I want to use this later on:

Client c1=new Client("Smith");

or

Client c1=new Client("Smith",20);

or 

Client c1=new Client("Smith",20,100);

How can I have optional parameters? Do I have to define constructors for each case? Thanks

Upvotes: 1

Views: 145

Answers (2)

Max Vasileuski
Max Vasileuski

Reputation: 2651

First answer is absolutely correct, but if you really want to have only one constructor for all these cases, you can write something like this:

public Client(String name, Integer age, Integer amount) {
    this.name = name;

    if (age != null) {
        this.age = age;
    }

    if (amount != null) {
        this.amount = amount;
    }
}

Usage:

Client c1 = new Client("Smith", null, null);
Client c2 = new Client("Smith", 20, null);
Client c3 = new Client("Smith", null, 100);
Client c4 = new Client(null, 20, 100);
Client c5 = new Client("Smith", 20, 100);

Pay attention that I used wrapper class Integer instead of int in constructor arguments because variable of int type can't be null.

Also, if you make your setters return this, you'll simulate kind of named arguments in Java:

new Client().setName("Smith").setAge(20).setAmount(100)

Upvotes: 1

Kon
Kon

Reputation: 10810

Yes, you have to overload the constructor, which is something you should read up on. It allows you to provide multiple input parameters for a method. The compiler will choose the appropriate method when the method is called.

Here are the Javadocs on overloading: http://docs.oracle.com/javase/tutorial/java/javaOO/methods.html

Upvotes: 7

Related Questions