Java :Setter Getter and constructor

Question

I\'m a bit confused about the use of getter/setters and constructors (see the below code for an example)

    public class ExampleClass {

        private in         


        

Answer 1

default constructor is always there

Well actually its not always there. A default constructor is the one which is provided by the compiler (of course it is a no-arg constructor ) Only if there is no other constructor defined in the class

why we use constructor with parameters to initialize values instead of set get

Because there could be a condition that an object can always be created only when all the values are provided at the time of initialization itself and there is no default value. So all values must be provided otherwise code will not compile.

Consider this Book class

public class Book {

    private String title;
    private String author;

    public Book(String title, String author){
        this.title = title;
        this.author = author;
    }
     //getters and setters here 
}

Consider a condition where a book can be created only if it has title and author.

• You cannot do new Book() because no-arg constructor is absent and compiler will not provide one because one constructor is already defined.
• Also you cannot do new Book() because our condition does not meet as every book requires a title and author.

This is the condition where parameterized constructor is useful.

Answer 2

My question is that if constructor is point of initialization and default constructor is always there so why we use constructor with parameters to initialize values instead of set get.

If you think about an object transitioning into different states then it makes sense to have a parameterized constructor alongwith setters and getters. Let me try to put a real life scenario: Think about an Employee class, a new employee joins, you don't know many details but few and you create the object of Employee with defualt and base value of its attributes. You need to register the employee in the system and hence you used the parameterized constructor. Once you get more details about the employee, you use getters and setters to update the attributes.

Answer 3

Just to make it easier. It takes less code to use a constructor than to create an object and use the setters.

Answer 4

Sometimes you don't need to set all the fields to specific values at the time of creating. For examle, when you make an array. Also, as already said, it's safer when you use getters -- you can't get nullpointer.

Remember to write the default constructor when you've defined constructor with parameters. Or be sure not to use it.

Answer 5

Because you write it using less, more elegant and better readable code when you set the values as parameters in a constructor. Moreover, sometimes some fields are indispensable for the object, so a parameter constructor prevents the user from creating an object omitting necessary fields for the object's functionality. One is though not "oblidged" to call the setters.